code: def obfn_g1var(self):
          r
  
          # Use of self.block_sep1(self.AXnr) instead of self.cnst_A1(self.X)
          # reduces number of calls to self.cnst_A0
          return self.var_y1() if self.opt['gEvalY'] else \
              self.block_sep1(self.AXnr)
docs: r"""Variable to be evaluated in computing the :math:`\ell_1`
          regularisation term, depending on the ``gEvalY`` option value.