code: def _create_online_model(self, lattice_instance, use_bl, mode='simu'):
          
          new_model = models.Models(name=use_bl, mode=mode)
          ele_name_list = lattice_instance.getElementList(use_bl)
          ele_eobj_list = []
          for ele in ele_name_list:
              ele_eobj_list.append(lattice_instance.makeElement(ele))
          new_model.addElement(*ele_eobj_list)
  
          return new_model
docs: make online model according to the lattice.Lattice instance
              :param lattice_instance: lattice.Lattice instance, created from lte/json file
              :param use_bl: selected beamline name
              :param simu: online modeling type, 'simu': simulation,
                           'online': online (incorporate control fields)