code: def register_obj_processors(self, obj_processors):
          
          self.obj_processors = obj_processors
          self.type_convertors.update(obj_processors)
docs: Object processors are callables that will be called after
          each successful model object construction.
          Those callables receive model object as its parameter.
          Registration of new object processors will replace previous.
  
          Args:
              obj_processors(dict): A dictionary where key=class name,
                  value=callable