
[;1m  digraph_to_family(Graph, Type)[0m

  Creates a family from the directed graph [;;4mGraph[0m. Each vertex a of [;;4m[0m
  [;;4mGraph[0m is represented by a pair (a, {b[1], ..., b[n]}), where the
  b[i]:s are the out-neighbors of a. It is assumed that [;;4mType[0m is a
  valid type of the external set of the family.

  If G is a directed graph, it holds that the vertices and edges of
  G are the same as the vertices and edges of [;;4m[0m
  [;;4mfamily_to_digraph(digraph_to_family(G))[0m.
