code: def test_cache(self, mock_cache_images):
      callback = imaging.ImagingCallback()
      callback.cache(10)
      mock_cache_images.assert_called_once_with(10)
  
imports: from unittest import TestCase
  from mock import MagicMock, patch, ANY
  import torch
  import torchbearer
  import torchbearer.callbacks.imaging
  import matplotlib.pyplot
label_desc: Use image node_id 2 for calling the TestImagingCallback obj's underlying member method code with example usage: obj.test_cache(mock_cache_images) without return types