code: def avg_pool(arr, block_size, cval=0, preserve_dtype=True):
      
      return pool(arr, block_size, np.average, cval=cval, preserve_dtype=preserve_dtype)
docs: Resize an array using average pooling.
  
      dtype support::
  
          See :func:`imgaug.imgaug.pool`.
  
      Parameters
      ----------
      arr : (H,W) ndarray or (H,W,C) ndarray
          Image-like array to pool. See :func:`imgaug.pool` for details.
  
      block_size : int or tuple of int or tuple of int
          Size of each block of values to pool. See :func:`imgaug.pool` for details.
  
      cval : number, optional
          Padding value. See :func:`imgaug.pool` for details.
  
      preserve_dtype : bool, optional
          Whether to preserve the input array dtype. See :func:`imgaug.pool` for details.
  
      Returns
      -------
      arr_reduced : (H',W') ndarray or (H',W',C') ndarray
          Array after average pooling.