code: def obfn_reg(self):
          r
  
          rl1 = np.linalg.norm((self.wl1 * self.obfn_gvar()).ravel(), 1)
          rl21 = np.sum(np.sqrt(np.sum(self.obfn_gvar()**2,
                                       axis=self.cri.axisC)))
          return (self.lmbda*rl1 + self.mu*rl21, rl1, rl21)
docs: r"""Compute regularisation terms and contribution to objective
          function. Regularisation terms are :math:`\| Y \|_1` and
          :math:`\| Y \|_{2,1}`.