docs: def memmap_array(self, dtype, shape, offset=0, mode='r', order='C'):
          """Return numpy.memmap of data stored in file."""
          if not self.is_file:
              raise ValueError('Cannot memory-map file without fileno')
          return numpy.memmap(self._fh, dtype=dtype, mode=mode,
                              offset=self._offset + offset,
                              shape=shape, order=order)