digraph Key {
  mindist = 2.0
  1 -> 2 [label="annotation"]
  1 -> 3 [label="selector"]
  2 -> 3 [label="selector"]
  3 -> 4 [label="field"]
  4 -> 4 [label="field"]
  1 [shape=circle, style=filled, color=blue]
  2 [shape=circle, style=filled, color=red]
  3 [shape=circle, style=filled, color=red]
  4 [shape=doublecircle, style=filled, color=green]
}