code: def test_handle_greyscale_input(mocker, model_grayscale):
      backprop = Backprop(model_grayscale)
  
      input_ = torch.zeros([1, 1, 224, 224], requires_grad=True)
  
      gradients = backprop.calculate_gradients(input_)
  
      assert gradients.shape == (1, 224, 224)
  
imports: import inspect
  import pytest
  import torch
  import torch.nn
  import torch.nn.functional
  import torchvision.models
  from flashtorch.saliency import Backprop
label_desc: Use image node_id 13 for calling a global function with example usage: test_handle_greyscale_input(mocker, model_grayscale) without return types