code: def cnst_AT(self, Y):
          r
  
          return self.cnst_A0T(self.block_sep0(Y)) + \
              np.sum(self.cnst_A1T(self.block_sep1(Y)), axis=-1)
docs: r"""Compute :math:`A^T \mathbf{y}`. In this case
          :math:`A^T \mathbf{y} = (I \;\; \Gamma_0^T \;\; \Gamma_1^T \;\;
          \ldots) \mathbf{y}`.