class_docstr: Commutation DAG tests.
code: def test_return_dag(self):
      def circuit():
          qml.PauliZ(wires=0)
  
      dag_object = qml.transforms.commutation_dag(circuit)()
      dag = dag_object.graph
  
      assert len(dag) != 0
  
file_path: pennylane/tests/transforms/test_commutation_dag.py
imports: from collections import OrderedDict
  import pytest
  from pennylane.wires import Wires
  import pennylane.numpy
  import pennylane
label_desc: Use image node_id 1 for calling the TestCommutationDAG obj's underlying member method code with example usage: obj.test_return_dag() without return types