code: def ystep(self):
          r
  
          AXU = self.AX + self.U
          Y0 = sp.prox_l1(self.block_sep0(AXU) - self.S, (1.0/self.rho)*self.W)
          Y1 = sp.prox_l1l2(self.block_sep1(AXU), 0.0,
                           (self.lmbda/self.rho)*self.wl21,
                           axis=self.cri.axisC)
          self.Y = self.block_cat(Y0, Y1)
          cbpdn.ConvTwoBlockCnstrnt.ystep(self)
docs: r"""Minimise Augmented Lagrangian with respect to
          :math:`\mathbf{y}`.