code: def operator(self):
          
          # is projection the zero operator?
          if self.V.shape[1] == 0:
              N = self.V.shape[0]
              return ZeroLinearOperator((N, N))
          return self._get_operator(self.apply, self.apply_adj)
docs: Get a ``LinearOperator`` corresponding to apply().
  
          :return: a LinearOperator that calls apply().