code: def K_pc_1(self):
          'Koopman operator on the modified basis (PC|1)'
          self._check_estimated()
          if not self._estimation_finished:
              self._finish_estimation()
          return self._f K_pc_1(self):
          'Koopman operator on the modified basis (PC|1)'
          self._check_estimated()
          if not self._estimation_finished:
              self._finish_estimation()
          return self._K
docs: Koopman operator on the modified basis (PC|1)