code: def area(masks):
      """Computes area of masks.
  
      Args:
        masks: Numpy array with shape [N, height, width] holding N masks. Masks
          values are of type np.uint8 and values are in {0,1}.
  
      Returns:
        a numpy array with shape [N*1] representing mask areas.
  
      Raises:
        ValueError: If masks.dtype is not np.uint8
      """
      if masks.dtype != np.uint8:
          raise ValueError("Masks type should be np.uint8")
      return np.sum(masks, axis=(1, 2), dtype=np.float32)
  
imports: from __future__ import absolute_import, division, print_function, unicode_literals
  import numpy
label_desc: Use image node_id 1 for calling a global function with example usage: area(masks) and returns: np