strict digraph M {
    subgraph "cluster_Top" {
        label=<<b>Top</b>>
        style="filled"
        fillcolor="/blues5/1"
        "customers" [shape=box,style="rounded,filled",fillcolor="/blues5/2",label=<<b>customers</b><br align="left"/>>];
        subgraph "cluster_grocery" {
            label=<<b>grocery</b>>
            style="filled"
            fillcolor="/blues5/2"
            "grocery.bagger0" [shape=box,style="rounded,filled",fillcolor="/blues5/3",label=<<b>bagger0</b><br align="left"/>>];
            subgraph "cluster_grocery.lane0" {
                label=<<b>lane0..lane1</b>>
                style="filled"
                fillcolor="/blues5/3"
                "grocery.lane0.cashier" [shape=box,style="rounded,filled",fillcolor="/blues5/4",label=<<b>cashier</b><br align="left"/>>];
            }
        }
    }
}