code: def test_custom_load_func(self):
      def load_fn(x):
          return x
  
      ic = ImageCollection(
          os.pathsep.join(self.pattern), load_func=load_fn
      )
      assert_equal(ic[0], self.pattern[0])
  
imports: import os
  import itertools
  import numpy
  import imageio.v3
  from skimage import data_dir
  from skimage.io.collection import ImageCollection, MultiImage, alphanumeric_key
  from skimage.io import reset_plugins
  from skimage._shared import testing
  from skimage._shared.testing import assert_equal, assert_allclose, fetch
  import pytest
label_desc: Use image node_id 8 for calling the TestImageCollection obj's underlying member method code with example usage: obj.test_custom_load_func() and returns: x