code: def test_vjp_is_unwrapped_for_param_shift():
      """Test that the intermediate vjps used by the batch Torch interface
      are unwrapped and no error is raised for a custom operation.
  
      Note: the execution flow of the operation resembles the implementation
      of the Kerr gate in Strawberry Fields as a similar example was failing
      for qml.Kerr and the strawberryfields.fock device.
      """
      nqubits = 2
  
      device = qml.device("default.qubit", wires=nqubits)
  
      class DummyOp(
          qml.operation.Operation
      ):  # pylint: disable=too-few-public-methods
          """Dummy operation."""
  
          num_wires = 1
          num_params = 1
  
          @staticmethod
          def compute_matrix(
              *params,
          ):  # pylint: disable=arguments-differ
              z = params[0]
              return np.diag([z, z])
  
      @qml.qnode(
          device=device,
          interface="torch",
          diff_method="parameter-shift",
      )
      def circ(inputs, w0):  # pylint: disable=unused-argument
          DummyOp(inputs[0], wires=0)
          return qml.expval(qml.PauliZ(0))
  
      weight_shapes = {"w0": (1)}
  
      qlayer = qml.qnn.TorchLayer(circ, weight_shapes)
      qlayers = torch.nn.Sequential(qlayer)
  
      x = torch.tensor([0.1], dtype=float, requires_grad=True)
      u = qlayers(x)
  
      u_x = torch.autograd.grad(
          u,
          x,
          grad_outputs=torch.ones_like(u, requires_grad=True),
          retain_graph=True,
          create_graph=True,
          allow_unused=True,
      )[0]
  
      assert isinstance(u_x, torch.Tensor)
  
imports: from unittest import mock
  import math
  from collections import defaultdict
  import numpy
  import pytest
  import pennylane
  from pennylane.qnn.torch import TorchLayer
label_desc: Use image node_id 4 for calling a global function with example usage: test_vjp_is_unwrapped_for_param_shift() and returns: qml, np