code: def can_reach(self, node, traversable=lambda node, edge: True):
          
          
          
          if isinstance(node, str):
              node = self.graph[node]
          for n in self.graph.nodes:
              n._visited = False
          return proximity.depth_first_search(self,
              visit=lambda n: node == n,
              traversable=traversable
              )
docs: Returns True if given node can be reached over traversable edges.
          To enforce edge direction, use a node==edge.node1 traversable.