def _bias_int2ext(self, bias_int: torch.Tensor) -> torch.Tensor:
        """
        >>> (); mod = sLSTMCell_cuda(
        ...     sLSTMCellConfig(hidden_size=64, num_heads=2), skip_backend_init=True); () # doctest:+ELLIPSIS
        (...)
        >>> torch.allclose(mod._bias_ext2int(mod._bias_int2ext(mod._bias)), mod._bias)
        True
        """

        return bias_int.reshape(
            self.config.num_heads, self.config.num_gates, self.config.head_dim
        )

        >>> (); mod = sLSTMCell_cuda(
        ...     sLSTMCellConfig(hidden_size=64, num_heads=2), skip_backend_init=True); () # doctest:+ELLIPSIS
        (...)
        >>> torch.allclose(mod._bias_ext2int(mod._bias_int2ext(mod._bias)), mod._bias)
        True
        
xlstm/blocks/slstm/cell.py