cluster example [graphviz]

digraph callgraph {

  node [fontname="verdana"];

  fontname="Verdana";

  subgraph cluster_foo {
     label="foo";
     node [label="method_1" ] foo_method_1;
     node [label="method_2" ] foo_method_2;
     node [label="method_3" ] foo_method_3;
  }

  subgraph cluster_bar {
    label="bar";
    node [label="method_a"  ] bar_method_a;
    node [label="method_b"  ] bar_method_b;
    node [label="method_c"  ] bar_method_c;
  }

  subgraph cluster_baz {
     label="baz";
     node [label="method_1" ] baz_method_1;
     node [label="method_b" ] baz_method_b;
     node [label="method_3" ] baz_method_3;
     node [label="method_c" ] baz_method_c;
  }

  main -> bar_method_a;

  bar_method_a -> bar_method_c;
  bar_method_a -> foo_method_2;

  foo_method_2 -> baz_method_3;

  bar_method_b -> foo_method_1;
  bar_method_b -> foo_method_2;
  baz_method_b -> baz_method_1;

  foo_method_2 -> foo_method_3;
  bar_method_c -> baz_method_c;
  bar_method_b -> baz_method_b;

  foo_method_1 -> baz_method_c;
}