underlyingGraph -- Returns the underlying graph of a digraph

• Usage:

  G = underlyingGraph D

• Inputs:
  • D, a digraph,
• Outputs:
  • G, a graph, The underlying graph of digraph D

i1 : D = digraph hashTable{1 => {2,3}, 2 => {1,3}, 3 => {}};

i2 : underlyingGraph D

o2 = Graph{1 => {2, 3}}
           2 => {1, 3}
           3 => {1, 2}

o2 : Graph