code: def ystep(self):
          r
  
          self.Y = np.asarray(sp.prox_l1l2(
              self.AX + self.U, (self.lmbda / self.rho) * self.wl1,
              self.mu / self.rho, axis=-1), dtype=self.dtype)
          GenericBPDN.ystep(self)
docs: r"""Minimise Augmented Lagrangian with respect to
          :math:`\mathbf{y}`.