code: def neighbors_iter(self, n, t=None):
          
          try:
              if t is None:
                  return iter(self._adj[n])
              else:
                  return iter([i for i in self._adj[n] if self.__presence_test(n, i, t)])
          except KeyError:
              raise nx.NetworkXError("The node %s is not in the graph." % (n,))
docs: Return an iterator over all neighbors of node n at time t.
  
          Parameters
          ----------
          n : node
             A node in the graph
          t : snapshot id (default=None)
              If None will be returned an iterator over the neighbors of the node on the flattened graph.
  
          Examples
          --------
          >>> G = dn.DynGraph()
          >>> G.add_path([0,1,2,3], t=0)
          >>> [n for n in G.neighbors_iter(0, t=0)]
          [1]