class_docstr: Test the transform function (validate and dispatch).
docstr: Test a device transform on old device.
code: def test_old_device_transform(self, valid_transform):
      """Test a device transform on old device."""
      dispatched_transform = transform(valid_transform)
      device = qml.device("default.mixed", wires=2)
      new_dev = dispatched_transform(device, index=0)
  
      assert isinstance(new_dev, type(device))
      assert new_dev.custom_expand_fn
      assert repr(device).startswith(
          "<DefaultMixed device (wires=2, shots=None)"
      )
      assert repr(new_dev).startswith(
          "<DefaultMixed device (wires=2, shots=None)"
      )
  
imports: from typing import Sequence, Callable
  from functools import partial
  import pytest
  import pennylane
  from pennylane.transforms.core import transform, TransformError, TransformContainer
label_desc: Use image node_id 19 for calling the TestTransformDispatcher obj's underlying member method code with example usage: obj.test_old_device_transform(valid_transform) without return types