old_contents: import numpy as np
  
  
  def assert_is_image(img, color=True, check_range=True):
      """Checks if an image satisfies image format.
  
      This function checks if a given image satisfies image format or not.
      If the image does not satifiy the format, this function raises an
      :class:`AssertionError`.
  
      Args:
          img (~numpy.ndarray): An image to be checked.
          color (bool): A boolean that determines the behaviour of
              channel(s) check. If it is :obj:`True`, the number of channels
              should be :obj:`3`. Otherwise, it should be :obj:`1`.
              The default value is :obj:`True`.
          check_range (bool): A boolean that determines whether the range
              of values are checked or not. If it is :obj:`True`,
              The values of image must be in :math:`[0, 255]`.
              Otherwise, this function does not check the range.
              The default value is :obj:`True`.
  
      """
  
      assert isinstance(img, np.ndarray), 'img must be a numpy.ndarray.'
      assert len(img.shape) == 3, 'img must be a 3-dimensional array.'
      C, H, W = img.shape
  
      if color:
          assert C == 3, 'The number of channels must be 3.'
      else:
          assert C == 1, 'The number of channels must be 1.'
  
      if check_range:
          assert img.min() >= 0 and img.max() <= 255, \
              'The values of img must be in [0, 255].'
  
new_contents: import numpy as np
  
  
  def assert_is_image(img, color=True, check_range=True):
      """Checks if an image satisfies image format.
  
      This function checks if a given image satisfies image format or not.
      If the image does not satifiy the format, this function raises an
      :class:`AssertionError`.
  
      Args:
          img (~numpy.ndarray): An image to be checked.
          color (bool): A boolean that determines the expected channel size.
              If it is :obj:`True`, the number of channels
              should be :obj:`3`. Otherwise, it should be :obj:`1`.
              The default value is :obj:`True`.
          check_range (bool): A boolean that determines whether the range
              of values are checked or not. If it is :obj:`True`,
              The values of image must be in :math:`[0, 255]`.
              Otherwise, this function does not check the range.
              The default value is :obj:`True`.
  
      """
  
      assert isinstance(img, np.ndarray), 'img must be a numpy.ndarray.'
      assert len(img.shape) == 3, 'img must be a 3-dimensional array.'
      C, H, W = img.shape
  
      if color:
          assert C == 3, 'The number of channels must be 3.'
      else:
          assert C == 1, 'The number of channels must be 1.'
  
      if check_range:
          assert img.min() >= 0 and img.max() <= 255, \
              'The values of img must be in [0, 255].'
  
subject: fix docs