code: def get_model_list(class_list):
      
      for idx, item in enumerate(class_list):
          if isinstance(item, six.string_types):
              model_class = apps.get_model(item)
              class_list[idx] = model_class
docs: Receives a list of strings with app_name.model_name format
      and turns them into classes. If an item is already a class
      it ignores it.