code: def ystep(self):
          r
  
          self.Y[..., 0:-1] = sp.prox_l2(
              self.AX[..., 0:-1] + self.U[..., 0:-1],
              (self.lmbda/self.rho)*self.Wtvna, axis=self.saxes)
          self.Y[..., -1] = sp.prox_l1(
              self.AX[..., -1] + self.U[..., -1] - self.S,
              (1.0/self.rho)*self.Wdf)
docs: r"""Minimise Augmented Lagrangian with respect to
          :math:`\mathbf{y}`.