def add_edge(self, graph_edge):
if not isinstance(graph_edge, Edge):<EOL><INDENT>raise TypeError('<STR_LIT>' + str(graph_edge))<EOL><DEDENT>edge_points = ( graph_edge.get_source(), graph_edge.get_destination() )<EOL>if edge_points in self.obj_dict['<STR_LIT>']:<EOL><INDENT>edge_list = self.obj_dict['<STR_LIT>'][edge_points]<EOL>edge_list.append(graph_edge.obj_dict)<EOL><DEDENT>else:<EOL><INDENT>self.obj_dict['<STR_LIT>'][edge_points] = [ graph_edge.obj_dict ]<EOL><DEDENT>graph_edge.set_sequence( self.get_next_sequence_number() )<EOL>graph_edge.set_parent_graph( self.get_parent_graph() )<EOL>
Adds an edge object to the graph.

        It takes a edge object as its only argument and returns
        None.