code: def has_interaction(self, u, v, t=None):
          
          try:
              if t is None:
                  return v in self._succ[u]
              else:
                  return v in self._succ[u] and self.__presence_test(u, v, t)
          except KeyError:
              return False
docs: Return True if the interaction (u,v) is in the graph at time t.
  
          Parameters
          ----------
          u, v : nodes
              Nodes can be, for example, strings or numbers.
              Nodes must be hashable (and not None) Python objects.
          t : snapshot id (default=None)
              If None will be returned the presence of the interaction on the flattened graph.
  
  
          Returns
          -------
          edge_ind : bool
              True if interaction is in the graph, False otherwise.
  
          Examples
          --------
          Can be called either using two nodes u,v or interaction tuple (u,v)
  
          >>> G = dn.DynDiGraph()
          >>> G.add_interaction(0,1, t=0)
          >>> G.add_interaction(1,2, t=0)
          >>> G.add_interaction(2,3, t=0)
          >>> G.has_interaction(0,1, t=0)
          True
          >>> G.has_interaction(0,1, t=1)
          False