Return a NetworkX Graph or DiGraph from a pygraphviz graph.
>>> G=nx.complete_graph(5)
>>> A=nx.to_agraph(G)
>>> X=nx.from_agraph(A)
The Graph X will have a dictionary X.graph_attr containing the default graphviz attributes for graphs, nodes and edges.
Default node attributes will be in the dictionary X.node_attr which is keyed by node.
Edge attributes will be returned as edge data in the graph X.
If you want a Graph with no attributes attached instead of an XGraph with attributes use
>>> G=nx.Graph(X)