Return the line graph of the graph or digraph G.
The line graph of a graph G has a node for each edge in G and an edge between those nodes if the two edges in G share a common node.
For DiGraphs an edge an edge represents a directed path of length 2.
The original node labels are kept as two-tuple node labels in the line graph.
| Parameters : | G : graph
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Notes
Not implemented for MultiGraph or MultiDiGraph classes.
Graph, node, and edge data are not propagated to the new graph.
Examples
>>> G=nx.star_graph(3)
>>> L=nx.line_graph(G)
>>> print(sorted(L.edges())) # makes a clique, K3
[((0, 1), (0, 2)), ((0, 1), (0, 3)), ((0, 3), (0, 2))]