def inverse(self):
inv = self.__class__()<EOL>inv.add_nodes(self.nodes())<EOL>inv.complete()<EOL>for each in self.edges():<EOL><INDENT>if (inv.has_edge(each)):<EOL><INDENT>inv.del_edge(each)<EOL><DEDENT><DEDENT>return inv<EOL>
Return the inverse of the graph.

@rtype:  graph
@return: Complement graph for the graph.