def block_cat(self, Y0, Y1):
        r"""Concatenate components corresponding to :math:`\mathbf{y}_0`
        and :math:`\mathbf{y}_1` to form :math:`\mathbf{y}\;\;`.
        """

        return np.concatenate((Y0, Y1), axis=self.blkaxis)
r"""Concatenate components corresponding to :math:`\mathbf{y}_0`
        and :math:`\mathbf{y}_1` to form :math:`\mathbf{y}\;\;`.