code: def load_system(cls, dict_, system_id='system'):
          
          obj = cls()
          obj.system = dict_
          obj.system_id = system_id
          return obj
docs: Create a :class:`MolecularSystem` from a python :class:`dict`.
  
          As the loaded :class:`MolecularSystem` is storred as a :class:`dict` in
          the :class:`MolecularSystem.system` it can also be loaded directly from
          a :class:`dict` input. This feature is used by :mod:`trajectory` that
          extracts trajectory frames as dictionaries and returns them
          as :class:`MolecularSystem` objects through this classmethod.
  
          Parameters
          ----------
          dict_ : :class:`dict`
             A python dictionary.
  
          system_id : :class:`str` or :class:'int', optional
             Inherited or user defined system id. (default='system')
  
          Returns
          -------
          :class:`pywindow.molecular.MolecularSystem`
              :class:`MolecularSystem`