code: def _add_input_state(self, node, input_state):
          
  
          successors = self._graph_visitor.successors(node)
  
          for succ in successors:
              if succ in self._state_map:
                  self._state_map[succ] = self._merge_states(succ, *([ self._state_map[succ], input_state ]))
              else:
                  self._state_map[succ] = input_state
docs: Add the input state to all successors of the given node.
  
          :param node:        The node whose successors' input states will be touched.
          :param input_state: The state that will be added to successors of the node.
          :return:            None