code: def get_q_df(self):
          '''
          getter
          '''
          if isinstance(self.__q_df, pd.DataFrame) is False and self.__q_df is not None:
              raise TypeError("The type of `__q_df` must be `pd.DataFrame`.")
          return self.__q_df get_q_df(self):
          '''
          getter
          '''
          if isinstance(self.__q_df, pd.DataFrame) is False and self.__q_df is not None:
              raise TypeError("The type of `__q_df` must be `pd.DataFrame`.")
          return self.__q_df
docs: getter