code: def test_get_length(test_images):
      with iio.get_reader(test_images / "chelsea.png") as file:
          v3_count = file.instance.properties(index=...).shape[0]
          assert len(file) == v3_count
  
file_path: imageio/tests/test_v2.py
imports: import pytest
  import imageio.v2
  import numpy
label_desc: Use image node_id 3 for calling a global function with example usage: test_get_length(test_images) without return types