code: def cnst_A0T(self, Y0):
          r
  
          # This calculation involves non-negligible computational cost. It
          # should be possible to disable relevant diagnostic information
          # (dual residual) to avoid this cost.
          Y0f = sl.rfftn(Y0, None, self.cri.axisN)
          return sl.irfftn(
              sl.dot(self.B.T, np.conj(self.Df) * Y0f, axis=self.cri.axisC),
                     self.cri.Nv, self.cri.axisN)
docs: r"""Compute :math:`A_0^T \mathbf{y}_0` component of
          :math:`A^T \mathbf{y}` (see :meth:`.ADMMTwoBlockCnstrnt.cnst_AT`).