code: def _get_chunk_indices(za):
      # TODO: does zarr provide code for this?
      
      return [(i, j) for i in range(int(math.ceil(float(za.shape[0])/za.chunks[0])))
              for j in range(int(math.ceil(float(za.shape[1])/za.chunks[1])))]
docs: Return all the indices (coordinates) for the chunks in a zarr array, even empty ones.