code: def test_boundless_mask_not_all_valid():
      """Confirm resolution of issue #1449"""
      with rasterio.open("tests/data/red.tif") as src:
          masked = src.read(
              1,
              boundless=True,
              masked=True,
              window=Window(-1, -1, 66, 66),
          )
      assert not masked.mask.all()
      assert masked.mask[:, 0].all()
      assert masked.mask[:, -1].all()
      assert masked.mask[0, :].all()
      assert masked.mask[-1, :].all()
  
imports: from affine import Affine
  import shutil
  from hypothesis import example, given
  import hypothesis.strategies
  import numpy
  from numpy.testing import assert_almost_equal
  import pytest
  import rasterio
  from rasterio.io import MemoryFile
  from rasterio.windows import Window
label_desc: Use image node_id 6 for calling a global function with example usage: test_boundless_mask_not_all_valid() without return types