Metadata-Version: 2.1
Name: cs.tagset
Version: 20230126
Summary: Tags and sets of tags with __format__ support and optional ontology information.
Home-page: https://bitbucket.org/cameron_simpson/css/commits/all
Author: Cameron Simpson
Author-email: Cameron Simpson <cs@cskk.id.au>
License: GNU General Public License v3 or later (GPLv3+)
Project-URL: URL, https://bitbucket.org/cameron_simpson/css/commits/all
Keywords: python3
Classifier: Programming Language :: Python
Classifier: Programming Language :: Python :: 3
Classifier: Development Status :: 4 - Beta
Classifier: Intended Audience :: Developers
Classifier: Operating System :: OS Independent
Classifier: Topic :: Software Development :: Libraries :: Python Modules
Classifier: License :: OSI Approved :: GNU General Public License v3 or later (GPLv3+)
Description-Content-Type: text/markdown

Tags and sets of tags
with __format__ support and optional ontology information.

*Latest release 20230126*:
New TagSet.is_stale() method based on .expiry attribute, intended for TagSets which are caches of other primary data.

See `cs.fstags` for support for applying these to filesystem objects
such as directories and files.

See `cs.sqltags` for support for databases of entities with tags,
not directly associated with filesystem objects.
This is suited to both log entries (entities with no "name")
and large collections of named entities;
both accept `Tag`s and can be searched on that basis.

All of the available complexity is optional:
you can use `Tag`s without bothering with `TagSet`s
or `TagsOntology`s.

This module contains the following main classes:
* `Tag`: an object with a `.name` and optional `.value` (default `None`)
  and also an optional reference `.ontology`
  for associating semantics with tag values.
  The `.value`, if not `None`, will often be a string,
  but may be any Python object.
  If you're using these via `cs.fstags`,
  the object will need to be JSON transcribeable.
* `TagSet`: a `dict` subclass representing a set of `Tag`s
  to associate with something;
  it also has setlike `.add` and `.discard` methods.
  As such it only supports a single `Tag` for a given tag name,
  but that tag value can of course be a sequence or mapping
  for more elaborate tag values.
* `TagsOntology`:
  a mapping of type names to `TagSet`s defining the type
  and also to entries for the metadata for specific per-type values.

Here's a simple example with some `Tag`s and a `TagSet`.

    >>> tags = TagSet()
    >>> # add a "bare" Tag named 'blue' with no value
    >>> tags.add('blue')
    >>> # add a "topic=tagging" Tag
    >>> tags.set('topic', 'tagging')
    >>> # make a "subtopic" Tag and add it
    >>> subtopic = Tag('subtopic', 'ontologies')
    >>> tags.add(subtopic)
    >>> # Tags have nice repr() and str()
    >>> subtopic
    Tag(name='subtopic',value='ontologies')
    >>> print(subtopic)
    subtopic=ontologies
    >>> # a TagSet also has a nice repr() and str()
    >>> tags
    TagSet:{'blue': None, 'topic': 'tagging', 'subtopic': 'ontologies'}
    >>> print(tags)
    blue subtopic=ontologies topic=tagging
    >>> tags2 = TagSet({'a': 1}, b=3, c=[1,2,3], d='dee')
    >>> tags2
    TagSet:{'a': 1, 'b': 3, 'c': [1, 2, 3], 'd': 'dee'}
    >>> print(tags2)
    a=1 b=3 c=[1,2,3] d=dee
    >>> # since you can print a TagSet to a file as a line of text
    >>> # you can get it back from a line of text
    >>> TagSet.from_line('a=1 b=3 c=[1,2,3] d=dee')
    TagSet:{'a': 1, 'b': 3, 'c': [1, 2, 3], 'd': 'dee'}
    >>> # because TagSets are dicts you can format strings with them
    >>> print('topic:{topic} subtopic:{subtopic}'.format_map(tags))
    topic:tagging subtopic:ontologies
    >>> # TagSets have convenient membership tests
    >>> # test for blueness
    >>> 'blue' in tags
    True
    >>> # test for redness
    >>> 'red' in tags
    False
    >>> # test for any "subtopic" tag
    >>> 'subtopic' in tags
    True
    >>> # test for subtopic=ontologies
    >>> print(subtopic)
    subtopic=ontologies
    >>> subtopic in tags
    True
    >>> # test for subtopic=libraries
    >>> subtopic2 = Tag('subtopic', 'libraries')
    >>> subtopic2 in tags
    False

## Ontologies

`Tag`s and `TagSet`s suffice to apply simple annotations to things.
However, an ontology brings meaning to those annotations.

See the `TagsOntology` class for implementation details,
access methods and more examples.

Consider a record about a movie, with these tags (a `TagSet`):

    title="Avengers Assemble"
    series="Avengers (Marvel)"
    cast={"Scarlett Johansson":"Black Widow (Marvel)"}

where we have the movie title,
a name for the series in which it resides,
and a cast as an association of actors with roles.

An ontology lets us associate implied types and metadata with these values.

Here's an example ontology supporting the above `TagSet`:

    type.cast type=dict key_type=person member_type=character description="members of a production"
    type.character description="an identified member of a story"
    type.series type=str
    character.marvel.black_widow type=character names=["Natasha Romanov"]
    person.scarlett_johansson fullname="Scarlett Johansson" bio="Known for Black Widow in the Marvel stories."

The type information for a `cast`
is defined by the ontology entry named `type.cast`,
which tells us that a `cast` `Tag` is a `dict`,
whose keys are of type `person`
and whose values are of type `character`.
(The default type is `str`.)

To find out the underlying type for a `character`
we look that up in the ontology in turn;
because it does not have a specified `type` `Tag`, it it taken to be a `str`.

Having the types for a `cast`,
it is now possible to look up the metadata for the described cast members.

The key `"Scarlett Johansson"` is a `person`
(from the type definition of `cast`).
The ontology entry for her is named `person.scarlett_johansson`
which is computed as:
* `person`: the type name
* `scarlett_johansson`: obtained by downcasing `"Scarlett Johansson"`
  and replacing whitespace with an underscore.
  The full conversion process is defined
  by the `TagsOntology.value_to_tag_name` function.

The key `"Black Widow (Marvel)"` is a `character`
(again, from the type definition of `cast`).
The ontology entry for her is named `character.marvel.black_widow`
which is computed as:
* `character`: the type name
* `marvel.black_widow`: obtained by downcasing `"Black Widow (Marvel)"`,
  replacing whitespace with an underscore,
  and moving a bracketed suffix to the front as an unbracketed prefix.
  The full conversion process is defined
  by the `TagsOntology.value_to_tag_name` function.

## Format Strings

You can just use `str.format_map` as shown above
for the direct values in a `TagSet`,
since it subclasses `dict`.

However, `TagSet`s also subclass `cs.lex.FormatableMixin`
and therefore have a richer `format_as` method which has an extended syntax
for the format component.
Command line tools like `fstags` use this for output format specifications.

An example:

    >>> # an ontology specifying the type for a colour
    >>> # and some information about the colour "blue"
    >>> ont = TagsOntology(
    ...   {
    ...       'type.colour':
    ...       TagSet(description="a colour, a hue", type="str"),
    ...       'colour.blue':
    ...       TagSet(
    ...           url='https://en.wikipedia.org/wiki/Blue',
    ...           wavelengths='450nm-495nm'
    ...       ),
    ...   }
    ... )
    >>> # tag set with a "blue" tag, using the ontology above
    >>> tags = TagSet(colour='blue', labels=['a', 'b', 'c'], size=9, _ontology=ont)
    >>> tags.format_as('The colour is {colour}.')
    'The colour is blue.'
    >>> # format a string about the tags showing some metadata about the colour
    >>> tags.format_as('Information about the colour may be found here: {colour:metadata.url}')
    'Information about the colour may be found here: https://en.wikipedia.org/wiki/Blue'

## Function `as_unixtime(tag_value)`

Convert a tag value to a UNIX timestamp.

This accepts `int`, `float` (already a timestamp)
and `date` or `datetime`
(use `datetime.timestamp() for a nonnaive `datetime`,
otherwise `time.mktime(tag_value.time_tuple())`,
which assumes the local time zone).

## Class `BaseTagSets(cs.resources.MultiOpenMixin, cs.context.ContextManagerMixin, collections.abc.MutableMapping, collections.abc.Mapping, collections.abc.Collection, collections.abc.Sized, collections.abc.Iterable, collections.abc.Container)`

Base class for collections of `TagSet` instances
such as `cs.fstags.FSTags` and `cs.sqltags.SQLTags`.

Examples of this include:
* `cs.fstags.FSTags`: a mapping of filesystem paths to their associated `TagSet`
* `cs.sqltags.SQLTags`: a mapping of names to `TagSet`s stored in an SQL database

Subclasses must implement:
* `get(name,default=None)`: return the `TagSet` associated
  with `name`, or `default`.
* `__setitem__(name,tagset)`: associate a `TagSet`with the key `name`;
  this is called by the `__missing__` method with a newly created `TagSet`.
* `keys(self)`: return an iterable of names

Subclasses may reasonably want to override the following:
* `startup_shutdown(self)`: context manager to allocate and release any
  needed resources such as database connections

Subclasses may implement:
* `__len__(self)`: return the number of names

The `TagSet` factory used to fetch or create a `TagSet` is
named `TagSetClass`. The default implementation honours two
class attributes:
* `TAGSETCLASS_DEFAULT`: initially `TagSet`
* `TAGSETCLASS_PREFIX_MAPPING`: a mapping of type names to `TagSet` subclasses

The type name of a `TagSet` name is the first dotted component.
For example, `artist.nick_cave` has the type name `artist`.
A subclass of `BaseTagSets` could utiliise an `ArtistTagSet` subclass of `TagSet`
and provide:

    TAGSETCLASS_PREFIX_MAPPING = {
      'artist': ArtistTagSet,
    }

in its class definition. Accesses to `artist.`* entities would
result in `ArtistTagSet` instances and access to other enitities
would result in ordinary `TagSet` instances.

*Method `BaseTagSets.__init__(self, *, ontology=None)`*:
Initialise the collection.

## Class `MappingTagSets(BaseTagSets, cs.resources.MultiOpenMixin, cs.context.ContextManagerMixin, collections.abc.MutableMapping, collections.abc.Mapping, collections.abc.Collection, collections.abc.Sized, collections.abc.Iterable, collections.abc.Container)`

A `BaseTagSets` subclass using an arbitrary mapping.

If no mapping is supplied, a `dict` is created for the purpose.

Example:

    >>> tagsets = MappingTagSets()
    >>> list(tagsets.keys())
    []
    >>> tagsets.get('foo')
    >>> tagsets['foo'] = TagSet(bah=1, zot=2)
    >>> list(tagsets.keys())
    ['foo']
    >>> tagsets.get('foo')
    TagSet:{'bah': 1, 'zot': 2}
    >>> list(tagsets.keys(prefix='foo'))
    ['foo']
    >>> list(tagsets.keys(prefix='bah'))
    []

## Class `RegexpTagRule`

A regular expression based `Tag` rule.

This applies a regular expression to a string
and returns inferred `Tag`s.

## Function `selftest(argv)`

Run some ad hoc self tests.

## Class `Tag(Tag, builtins.tuple, cs.lex.FormatableMixin, cs.lex.FormatableFormatter, string.Formatter)`

A `Tag` has a `.name` (`str`) and a `.value`
and an optional `.ontology`.

The `name` must be a dotted identifier.

Terminology:
* A "bare" `Tag` has a `value` of `None`.
* A "naive" `Tag` has an `ontology` of `None`.

The constructor for a `Tag` is unusual:
* both the `value` and `ontology` are optional,
  defaulting to `None`
* if `name` is a `str` then we always construct a new `Tag`
  with the suppplied values
* if `name` is not a `str`
  it should be a `Tag`like object to promote;
  it is an error if the `value` parameter is not `None`
  in this case
* an optional `prefix` may be supplied
  which is prepended to `name` with a dot (`'.'`) if not empty

The promotion process is as follows:
* if `name` is a `Tag` subinstance
  then if the supplied `ontology` is not `None`
  and is not the ontology associated with `name`
  then a new `Tag` is made,
  otherwise the original `Tag` is returned unchanged
* otherwise a new `Tag` is made from `name`
  using its `.value`
  and overriding its `.ontology`
  if the `ontology` parameter is not `None`

Examples:

    >>> ont = TagsOntology({'colour.blue': TagSet(wavelengths='450nm-495nm')})
    >>> tag0 = Tag('colour', 'blue')
    >>> tag0
    Tag(name='colour',value='blue')
    >>> tag = Tag(tag0)
    >>> tag
    Tag(name='colour',value='blue')
    >>> tag = Tag(tag0, ontology=ont)
    >>> tag # doctest: +ELLIPSIS
    Tag(name='colour',value='blue',ontology=...)
    >>> tag = Tag(tag0, prefix='surface')
    >>> tag
    Tag(name='surface.colour',value='blue')

*Method `Tag.__init__(self, *a, **kw)`*:
Dummy `__init__` to avoid `FormatableMixin.__init__`
because we subclass `namedtuple` which has no `__init__`.

## Function `tag_or_tag_value(*da, **dkw)`

A decorator for functions or methods which may be called as:

    func(name[,value])

or as:

    func(Tag)

The optional decorator argument `no_self` (default `False`)
should be supplied for plain functions
as they have no leading `self` parameter to accomodate.

Example:

    @tag_or_tag_value
    def add(self, tag_name, value, *, verbose=None):

This defines a `.add()` method
which can be called with `name` and `value`
or with single `Tag`like object
(something with `.name` and `.value` attributes),
for example:

    tags = TagSet()
    ....
    tags.add('colour', 'blue')
    ....
    tag = Tag('size', 9)
    tags.add(tag)

## Class `TagBasedTest(TagBasedTest, builtins.tuple, TagSetCriterion)`

A test based on a `Tag`.

Attributes:
* `spec`: the source text from which this choice was parsed,
  possibly `None`
* `choice`: the apply/reject flag
* `tag`: the `Tag` representing the criterion
* `comparison`: an indication of the test comparison

The following comparison values are recognised:
* `None`: test for the presence of the `Tag`
* `'='`: test that the tag value equals `tag.value`
* `'<'`: test that the tag value is less than `tag.value`
* `'<='`: test that the tag value is less than or equal to `tag.value`
* `'>'`: test that the tag value is greater than `tag.value`
* `'>='`: test that the tag value is greater than or equal to `tag.value`
* `'~/'`: test if the tag value as a regexp is present in `tag.value`
* '~': test if a matching tag value is present in `tag.value`

## Class `TagFile(cs.fs.FSPathBasedSingleton, cs.obj.SingletonMixin, cs.fs.HasFSPath, BaseTagSets, cs.resources.MultiOpenMixin, cs.context.ContextManagerMixin, collections.abc.MutableMapping, collections.abc.Mapping, collections.abc.Collection, collections.abc.Sized, collections.abc.Iterable, collections.abc.Container)`

A reference to a specific file containing tags.

This manages a mapping of `name` => `TagSet`,
itself a mapping of tag name => tag value.

## Class `TagsCommandMixin`

Utility methods for `cs.cmdutils.BaseCommand` classes working with tags.

Optional subclass attributes:
* `TAGSET_CRITERION_CLASS`: a `TagSetCriterion` duck class,
  default `TagSetCriterion`.
  For example, `cs.sqltags` has a subclass
  with an `.extend_query` method for computing an SQL JOIN
  used in searching for tagged entities.

## Class `TagSet(builtins.dict, cs.dateutils.UNIXTimeMixin, cs.lex.FormatableMixin, cs.lex.FormatableFormatter, string.Formatter, cs.mappings.AttrableMappingMixin)`

A setlike class associating a set of tag names with values.

This actually subclasses `dict`, so a `TagSet` is a direct
mapping of tag names to values.
It accepts attribute access to simple tag values when they
do not conflict with the class methods;
the reliable method is normal item access.

*NOTE*: iteration yields `Tag`s, not dict keys.

Also note that all the `Tags` from a `TagSet`
share its ontology.

Subclasses should override the `set` and `discard` methods;
the `dict` and mapping methods
are defined in terms of these two basic operations.

`TagSet`s have a few special properties:
* `id`: a domain specific identifier;
  this may reasonably be `None` for entities
  not associated with database rows;
  the `cs.sqltags.SQLTags` class associates this
  with the database row id.
* `name`: the entity's name;
  a read only alias for the `'name'` `Tag`.
  The `cs.sqltags.SQLTags` class defines "log entries"
  as `TagSet`s with no `name`.
* `unixtime`: a UNIX timestamp,
  a `float` holding seconds since the UNIX epoch
  (midnight, 1 January 1970 UTC).
  This is typically the row creation time
  for entities associated with database rows,
  but usually the event time for `TagSet`s describing an event.

Because ` TagSet` subclasses `cs.mappings.AttrableMappingMixin`
you can also access tag values as attributes
*provided* that they do not conflict with instance attributes
or class methods or properties.
The `TagSet` class defines the class attribute `ATTRABLE_MAPPING_DEFAULT`
as `None` which causes attribute access to return `None`
for missing tag names.
This supports code like:

    if tags.title:
        # use the title in something
    else:
        # handle a missing title tag

*Method `TagSet.__init__(self, *a, _id=None, _ontology=None, **kw)`*:
Initialise the `TagSet`.

Parameters:
* positional parameters initialise the `dict`
  and are passed to `dict.__init__`
* `_id`: optional identity value for databaselike implementations
* `_ontology`: optional `TagsOntology to use for this `TagSet`
* other alphabetic keyword parameters are also used to initialise the
  `dict` and are passed to `dict.__init__`

## Class `TagSetCriterion`

A testable criterion for a `TagSet`.

## Class `TagSetPrefixView(cs.lex.FormatableMixin, cs.lex.FormatableFormatter, string.Formatter)`

A view of a `TagSet` via a `prefix`.

Access to a key `k` accesses the `TagSet`
with the key `prefix+'.'+k`.

This is a kind of funny hybrid of a `Tag` and a `TagSet`
in that some things such as `__format__`
will format the `Tag` named `prefix` if it exists
in preference to the subtags.

Example:

    >>> tags = TagSet(a=1, b=2)
    >>> tags
    TagSet:{'a': 1, 'b': 2}
    >>> tags['sub.x'] = 3
    >>> tags['sub.y'] = 4
    >>> tags
    TagSet:{'a': 1, 'b': 2, 'sub.x': 3, 'sub.y': 4}
    >>> sub = tags.sub
    >>> sub
    TagSetPrefixView:sub.{'x': 3, 'y': 4}
    >>> sub.z = 5
    >>> sub
    TagSetPrefixView:sub.{'x': 3, 'y': 4, 'z': 5}
    >>> tags
    TagSet:{'a': 1, 'b': 2, 'sub.x': 3, 'sub.y': 4, 'sub.z': 5}

## Class `TagSetsSubdomain(cs.obj.SingletonMixin, cs.mappings.PrefixedMappingProxy, cs.mappings.RemappedMappingProxy)`

A view into a `BaseTagSets` for keys commencing with a prefix
being the subdomain plus a dot (`'.'`).

## Class `TagsOntology(cs.obj.SingletonMixin, BaseTagSets, cs.resources.MultiOpenMixin, cs.context.ContextManagerMixin, collections.abc.MutableMapping, collections.abc.Mapping, collections.abc.Collection, collections.abc.Sized, collections.abc.Iterable, collections.abc.Container)`

An ontology for tag names.
This is based around a mapping of names
to ontological information expressed as a `TagSet`.

Normally an object's tags are not a self contained repository of all the information;
instead a tag just names some information.

As a example, consider the tag `colour=blue`.
Meta information about `blue` is obtained via the ontology,
which has an entry for the colour `blue`.
We adopt the convention that the type is just the tag name,
so we obtain the metadata by calling `ontology.metadata(tag)`
or alternatively `ontology.metadata(tag.name,tag.value)`
being the type name and value respectively.

The ontology itself is based around `TagSets` and effectively the call
`ontology.metadata('colour','blue')`
would look up the `TagSet` named `colour.blue` in the underlying `Tagsets`.

For a self contained dataset this means that it can be its own ontology.
For tags associated with arbitrary objects
such as the filesystem tags maintained by `cs.fstags`
the ontology would be a separate tags collection stored in a central place.

There are two main categories of entries in an ontology:
* metadata: other entries named *typename*`.`*value_key*
  contains a `TagSet` holding metadata for a value of type *typename*
  whose value is mapped to *value_key*
* types: an optional entry named `type.`*typename* contains a `TagSet`
  describing the type named *typename*;
  really this is just more metadata where the "type name" is `type`

Metadata are `TagSets` instances describing particular values of a type.
For example, some metadata for the `Tag` `colour="blue"`:

    colour.blue url="https://en.wikipedia.org/wiki/Blue" wavelengths="450nm-495nm"

Some metadata associated with the `Tag` `actor="Scarlett Johansson"`:

    actor.scarlett_johansson role=["Black Widow (Marvel)"]
    character.marvel.black_widow fullname=["Natasha Romanov"]

The tag values are lists above because an actor might play many roles, etc.

There's a convention for converting human descriptions
such as the role string `"Black Widow (Marvel)"` to its metadata.
* the value `"Black Widow (Marvel)"` if converted to a key
  by the ontology method `value_to_tag_name`;
  it moves a bracket suffix such as `(Marvel)` to the front as a prefix
  `marvel.` and downcases the rest of the string and turns spaces into underscores.
  This yields the value key `marvel.black_widow`.
* the type is `role`, so the ontology entry for the metadata
  is `role.marvel.black_widow`

This requires type information about a `role`.
Here are some type definitions supporting the above metadata:

    type.person type=str description="A person."
    type.actor type=person description="An actor's stage name."
    type.character type=str description="A person in a story."
    type.role type_name=character description="A character role in a performance."
    type.cast type=dict key_type=actor member_type=role description="Cast members and their roles."

The basic types have their Python names: `int`, `float`, `str`, `list`,
`dict`, `date`, `datetime`.
You can define subtypes of these for your own purposes
as illustrated above.

For example:

    type.colour type=str description="A hue."

which subclasses `str`.

Subtypes of `list` include a `member_type`
specifying the type for members of a `Tag` value:

    type.scene type=list member_type=str description="A movie scene."

Subtypes of `dict` include a `key_type` and a `member_type`
specifying the type for keys and members of a `Tag` value:

Accessing type data and metadata:

A `TagSet` may have a reference to a `TagsOntology` as `.ontology`
and so also do any of its `Tag`s.

## Class `TagsOntologyCommand(cs.cmdutils.BaseCommand)`

A command line for working with ontology types.

Command line usage:

    Usage: tagsontology subcommand [...]
      Subcommands:
        edit [{/name-regexp | entity-name}]
          Edit entities.
          With no arguments, edit all the entities.
          With an argument starting with a slash, edit the entities
          whose names match the regexp.
          Otherwise the argument is expected to be an entity name;
          edit the tags of that entity.
        help [-l] [subcommand-names...]
          Print the full help for the named subcommands,
          or for all subcommands if no names are specified.
          -l  Long help even if no subcommand-names provided.
        meta tag=value
        type
            With no arguments, list the defined types.
          type type_name
            With a type name, print its `Tag`s.
          type type_name edit
            Edit the tags defining a type.
          type type_name edit meta_names_pattern...
            Edit the tags for the metadata names matching the
            meta_names_patterns.
          type type_name list
          type type_name ls
            List the metadata names for this type and their tags.
          type type_name + entity_name [tags...]
            Create type_name.entity_name and apply the tags.

# Release Log



*Release 20230126*:
New TagSet.is_stale() method based on .expiry attribute, intended for TagSets which are caches of other primary data.

*Release 20221228*:
* TagFile: drop _singleton_key, FSPathBasedSingleton provides a good default.
* TagFile.save_tagsets,tags_line: new optional prune=False parameter to drop empty top level dict/lists.
* TagFile.save: plumb prune=False parameter.

*Release 20220806*:
New TagSetCriterion.promote(obj)->TagSetCriterion class method.

*Release 20220606*:
* Tag.parse_value: bugfix parse of float.
* TagSet.edit: accept optional comments parameter with addition header comment lines, be more tolerant of errors, avoid losing data on error.

*Release 20220430*:
* TagSetPrefixView: new as_dict() method.
* TagSetPrefixView.__str__: behave like TagSet.__str__.
* TagFile.save_tagsets: do not try to save if the file is missing and the tagsets are empty.
* New TagSet.from_tags(tags) factory to make a new TagSet from an iterable of tags.
* TagSetPrefixView: add .get and .setdefault mapping methods.
* RegexpTagRule: accept optional tag_prefix parameter.
* Tagset: new from_ini() and save_as_ini() methods to support cs.timeseries config files, probably handy elsewhere.

*Release 20220311*:
Assorted internal changes.

*Release 20211212*:
* Tag: new fallback_parse parameter for value parsing, default get_nonwhite.
* Tag: new from_arg factory with fallback_parse grabbing the whole string for command line arguments, thus supporting unquoted strings for ease of use.
* TagSetCriterion: new optional fallback_parse parameter and from_arg method as for the Tag factories.
* Tag.transcribe_value: accept optional json_options to control the JSON encoder, used for human friendly multiline edits in cs.app.tagger.
* Rename edit_many to edit_tagsets for clarity.
* TagsOntology: new type_values method to return values for a type (derived from their metadata entries).
* Tag: new alt_values method returning its TagsOntology.type_values.
* (Internal) New _FormatStringTagProxy which proxies a Tag but uses str(self.__proxied.value) for __str__ to support format strings.
* (Internal) TagSet.get_value: if arg_name matches a Tag, return a _FormatStringTagProxy.
* Tag.__new__: accept (tag_name,value) or (Tag) as initialisation parameters.

*Release 20210913*:
* TagSet.get_value: raise KeyError in strict mode, leave placeholder otherwise.
* Other small changes.

*Release 20210906*:
Many many updates; some semantics have changed.

*Release 20210428*:
Bugfix TagSet.set: internal in place changes to a complex tag value were not noticed, causing TagFile to not update on shutdown.

*Release 20210420*:
* TagSet: also subclass cs.dateutils.UNIXTimeMixin.
* Various TagSetNamespace updates and bugfixes.

*Release 20210404*:
Bugfix TagBasedTest.COMPARISON_FUNCS["="]: if cmp_value is None, return true (the tag is present).

*Release 20210306*:
* ExtendedNamespace,TagSetNamespace: move the .[:alpha:]* attribute support from ExtendedNamespace to TagSetNamespace because it requires Tags.
* TagSetNamespace.__getattr__: new _i, _s, _f suffixes to return int, str or float tag values (or None); fold _lc in with these.
* Pull most of `TaggedEntity` out into `TaggedEntityMixin` for reuse by domain specific tagged entities.
* TaggedEntity: new .set and .discard methods.
* TaggedEntity: new as_editable_line, from_editable_line, edit and edit_entities methods to support editing entities using a text editor.
* ontologies: type entries are now prefixed with "type." and metadata entries are prefixed with "meta."; provide a worked ontology example in the introduction and improve related docstrings.
* TagsOntology: new .types(), .types_names(), .meta(type_name,value), .meta_names() methods.
* TagsOntology.__getitem__: create missing TagSets on demand.
* New TagsOntologyCommand, initially with a "type [type_name [{edit|list}]]" subcommand, ready for use as the cmd_ont subcommand of other tag related commands.
* TagSet: support initialisation like a dict including keywords, and move the `ontology` parameter to `_onotology`.
* TagSet: include AttrableMappingMixin to enable attribute access to values when there is no conflict with normal methods.
* UUID encode/decode support.
* Honour $TAGSET_EDITOR or $EDITOR as preferred interactive editor for tags.
* New TagSet.subtags(prefix) to extract a subset of the tags.
* TagsOntology.value_metadata: new optional convert parameter to override the default "convert human friendly name" algorithm, particularly to pass convert=str to things which are already the basic id.
* Rename TaggedEntity to TagSet.
* Rename TaggedEntities to TagSets.
* TagSet: new csvrow and from_csvrow methods imported from obsolete TaggedEntityMixin class.
* Move BaseTagFile from cs.fstags to TagFile in cs.tagset.
* TagSet: support access to the tag "c.x" via attributes provided there is no "c" tag in the way.
* TagSet.unixtime: implement the autoset-to-now semantics.
* New as_timestamp(): convert date, datetime, int or float to a UNIX timestamp.
* Assorted docstring updates and bugfixes.

*Release 20200716*:
* Update for changed cs.obj.SingletonMixin API.
* Pull in TaggedEntity from cs.sqltags and add the .csvrow property and the .from_csvrow factory.

*Release 20200521.1*:
Fix DISTINFO.install_requires, drop debug import.

*Release 20200521*:
* New ValueDetail and KeyValueDetail classes for returning ontology information; TagInfo.detail now returns a ValueDetail for scalar types, a list of ValueDetails for sequence types and a list of KeyValueDetails for mapping types; drop various TagInfo mapping/iterable style methods, too confusing to use.
* Plumb ontology parameter throughout, always optional.
* Drop TypedTag, Tags now use ontologies for this.
* New TagsCommandMixin to support BaseCommands which manipulate Tags.
* Many improvements and bugfixes.

*Release 20200318*:
* *Note that the TagsOntology stuff is in flux and totally alpha.*
* Tag.prefix_name factory returning a new tag if prefix is not empty, ptherwise self.
* TagSet.update: accept an optional prefix for inserting "foreign" tags with a distinguishing name prefix.
* Tag.as_json: turn sets and tuples into lists for encoding.
* Backport for Python < 3.7 (no fromisoformat functions).
* TagSet: drop unused and illplaced .titleify, .episode_title and .title methods.
* TagSet: remove "defaults", unused.
* Make TagSet a direct subclass of dict, adjust uses of .update etc.
* New ExtendedNamespace class which is a SimpleNamespace with some inferred attributes and a partial mapping API (keys and __getitem__).
* New TagSet.ns() returning the Tags as an ExtendedNamespace, which doubles as a mapping for str.format_map; TagSet.format_kwargs is now an alias for this.
* New Tag.from_string factory to parse a str into a Tag.
* New TagsOntology and TypedTag classes to provide type and value-detail information; very very alpha and subject to change.

*Release 20200229.1*:
Initial release: pull TagSet, Tag, TagChoice from cs.fstags for independent use.
