code: def rsdl_rn(self, AX, Y):
          
  
          # Avoid computing the norm of the value returned by cnst_c()
          # more than once
          if not hasattr(self, '_nrm_cnst_c'):
              self._nrm_cnst_c = np.linalg.norm(self.cnst_c())
          return max((np.linalg.norm(AX), np.linalg.norm(self.cnst_B(Y)),
                      self._nrm_cnst_c))
docs: Compute primal residual normalisation term.
  
          Overriding this method is required if methods :meth:`cnst_A`,
          :meth:`cnst_AT`, :meth:`cnst_B`, and :meth:`cnst_c` are not
          overridden.