Return an undirected representation of the digraph.
Returns:
G : MultiGraph
An undirected graph with the same name and nodes and
with edge (u,v,data) if either (u,v,data) or (v,u,data)
is in the digraph. If both edges exist in digraph and
their edge data is different, only one edge is created
with an arbitrary choice of which edge data to use.
You must check and correct for this manually if desired.
Notes
This is similar to MultiGraph(self) which returns a shallow copy.
self.to_undirected() returns a deepcopy of edge, node and
graph attributes.