def METHOD_NAME(self, members, ident=None):
    '''
    Optional resource sets.
    '''
    sg_obj = SubgraphDot(ident)
    e_id = sg_obj.new_edge(members)
    sg_obj.new_edge_attr(e_id, 'style', 'invis')
    sg_obj.new_edge_attr(e_id, 'constraint', 'false')
    self.subgraphs.append(sg_obj)
    return sg_obj