code: def test_files_property(self):
      assert isinstance(self.images.files, list)
  
      def set_files(f):
          self.images.files = f
  
      with testing.raises(AttributeError):
          set_files("newfiles")
  
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 5 for calling the TestImageCollection obj's underlying member method code with example usage: obj.test_files_property() without return types