docs: def addNodeLabelPrefix(self, prefix=None, copy=False):
          '''
          Rename all nodes in the network from x to prefix_x.  If no prefix
          is given, use the name of the graph as the prefix.
          
          The purpose of this method is to make node names unique so that
          composing two graphs is well-defined.
          '''
          nxgraph = Topology.__relabel_graph(self.__nxgraph, prefix)
          if copy:
              newtopo = copy.deepcopy(self)
              newtopo.nxgraph = nxgraph
              return newtopo
          else:
              # looks like it was done in place
              self.__nxgraph = nxgraph