code: def getSubgraphList(self, parent_name):
          
          if not self.isMultigraph:
              raise AttributeError("Simple Munin Plugins cannot have subgraphs.")
          if self._graphDict.has_key(parent_name):
              return self._subgraphNames[parent_name] or []
          else:
              raise AttributeError("Invalid parent graph name %s."
                                   % (parent_name,))
docs: Returns list of names of subgraphs for Root Graph with name parent_name.
          
          @param parent_name: Name of Root Graph.
          @return:            List of subgraph names.