code: def test_warning_shadow(tiffs):
      """Shadow warning is raised"""
      filename = str(tiffs.join("shadowed.tif"))
      with rasterio.open(filename) as src:
          with pytest.warns(NodataShadowWarning):
              src.read_masks()
  
file_path: rasterio/tests/test_band_masks.py
imports: import numpy
  import pytest
  import rasterio
  from rasterio.enums import MaskFlags
  from rasterio.errors import NodataShadowWarning
label_desc: Use image node_id 7 for calling a global function with example usage: test_warning_shadow(tiffs) without return types