code: def test_len(self):
      assert len(self.images) == 2
  
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 2 for calling the TestImageCollection obj's underlying member method code with example usage: obj.test_len() without return types