code: def test_read_label_mutable(self):
      img = read_label(self.file, dtype=self.dtype)
      img[:] = 0
      np.testing.assert_equal(img, 0)
  
file_path: chainercv/tests/utils_tests/image_tests/test_read_label.py
imports: import numpy
  import tempfile
  import unittest
  from chainer import testing
  from chainercv.utils import read_label
  from chainercv.utils import write_image
label_desc: Use image node_id 3 for calling the TestReadLabel obj's underlying member method code with example usage: obj.test_read_label_mutable() without return types