add controlflow handling to stochastic swap pass

qiskit/dagcircuit/dagcircuit.py

@@ -34,6 +34,7 @@
 from qiskit.circuit.gate import Gate
 from qiskit.circuit.instruction import Instruction
 from qiskit.circuit.parameterexpression import ParameterExpression
+from qiskit.circuit.controlflow import ControlFlowOp
 from qiskit.dagcircuit.exceptions import DAGCircuitError
 from qiskit.dagcircuit.dagnode import DAGNode, DAGOpNode, DAGInNode, DAGOutNode
 from qiskit.utils import optionals as _optionals
@@ -1438,6 +1439,10 @@ def multi_qubit_ops(self):
                 ops.append(node)
         return ops
 
+    def control_flow_ops(self):
+        """return control flow operations"""
+        return self.op_nodes(op=ControlFlowOp)
+
     def longest_path(self):
         """Returns the longest path in the dag as a list of DAGOpNodes, DAGInNodes, and DAGOutNodes."""
         return [self._multi_graph[x] for x in rx.dag_longest_path(self._multi_graph)]