def del_edge(self, edge):
u, v = edge<EOL>self.node_neighbors[u].remove(v)<EOL>self.del_edge_labeling((u, v))  <EOL>if (u != v):<EOL><INDENT>self.node_neighbors[v].remove(u)<EOL>self.del_edge_labeling((v, u))<EOL><DEDENT>
Remove an edge from the graph.

@type  edge: tuple
@param edge: Edge.