docstr: Test diagonalizing_gates method with and observable.
docstr_tok: ["Test","diagonalizing_gates","method","with","and","observable","."]
code: def test_obs_diagonalizing_gates(self):
      """Test diagonalizing_gates method with and observable."""
      m = qml.expval(qml.PauliY(0))
  
      res = m.diagonalizing_gates()
  
      assert len(res) == 3
  
      expected_classes = [qml.PauliZ, qml.S, qml.Hadamard]
      for op, c in zip(res, expected_classes):
          assert isinstance(op, c)
  
imports: import numpy
  import pytest
  import pennylane
  from pennylane.measurements import ClassicalShadowMP, Counts, CountsMP, Expectation, ExpectationMP, MeasurementProcess, MeasurementTransform, MeasurementValue, MidMeasure, MidMeasureMP, MutualInfoMP, PurityMP, Probability, ProbabilityMP, Sample, SampleMeasurement, SampleMP, ShadowExpvalMP, Shots, State, StateMeasurement, StateMP, Variance, VarianceMP, VnEntropyMP, expval, sample, var
  from pennylane.operation import DecompositionUndefinedError
  from pennylane.queuing import AnnotatedQueue
  from pennylane.wires import Wires
label_desc: Use image node_id 2 for calling the TestDiagonalizingGates obj's underlying member method code with example usage: obj.test_obs_diagonalizing_gates() without return types