def quantum_successors(self, node):
        """Returns list of the successors of a node that are
        connected by a quantum edge as DAGNodes."""
        if isinstance(node, int):
            warnings.warn('Calling quantum_successors() with a node id is deprecated,'
                          ' use a DAGNode instead',
                          DeprecationWarning, 2)
            node = self._id_to_node[node]

        successors = []
        for successor in self.successors(node):
            if isinstance(self._multi_graph.get_edge_data(
                    node, successor, key=0)['wire'][0],
                          QuantumRegister):
                successors.append(successor)
        return successors
Returns list of the successors of a node that are
        connected by a quantum edge as DAGNodes.