code: def zero_pixels(self):
          
          zero_px = np.where(np.sum(self.raw_data, axis=2) == 0)
          zero_px = np.c_[zero_px[0], zero_px[1]]
          return zero_px
docs: Return an array of the zero pixels.
  
          Returns
          -------
          :obj:`numpy.ndarray`
               Nx2 array of the zero pixels