code: def _name_things(self):
          
          edges = {}
          nodes = {None: 'root'}
          for n in self._tree.postorder_node_iter():
              nodes[n] = '.'.join([str(x.taxon) for x in n.leaf_nodes()])
          for e in self._tree.preorder_edge_iter():
              edges[e] = ' ---> '.join([nodes[e.tail_node], nodes[e.head_node]])
  
          r_edges = {value: key for key, value in edges.items()}
          r_nodes = {value: key for key, value in nodes.items()}
          return edges, nodes, r_edges, r_nodes
docs: Easy names for debugging