code: def ystep(self):
          r
  
          self.Y = sp.prox_l1l2(self.AX + self.U, (self.lmbda/self.rho)*self.wl1,
                               (self.mu/self.rho), axis=self.cri.axisC)
          cbpdn.GenericConvBPDN.ystep(self)
docs: r"""Minimise Augmented Lagrangian with respect to
          :math:`\mathbf{y}`.