code: def _radial_distance(shape):
      
  
      if len(shape) != 2:
          raise ValueError('shape must have only 2 elements')
      position = (np.asarray(shape) - 1) / 2.
      x = np.arange(shape[1]) - position[1]
      y = np.arange(shape[0]) - position[0]
      xx, yy = np.meshgrid(x, y)
      return np.sqrt(xx**2 + yy**2)
docs: Return an array where each value is the Euclidean distance from the
      array center.
  
      Parameters
      ----------
      shape : tuple of int
          The size of the output array along each axis.
  
      Returns
      -------
      result : `~numpy.ndarray`
          An array containing the Euclidian radial distances from the
          array center.