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

def _add_input_state(self, node, input_state):
        """
        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
        """

        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