code: def load_tt_dict(self, locale, tt_d):
          
          
          #/ get the old tt dict of the locale
          tt_d_old = self.tt_dd.get(locale, None)
          
          #/ if has old tt dict
          ## N
          if tt_d_old is None:
              #/ use the new tt dict
              self.tt_dd[locale] = tt_d
          ## Y
          else:
              #/ update the old tt dict
              tt_d_old.update(tt_d)
docs: Load a tt dict into |self.tt_dd|.
          |tt| means text transform.
          
          locale: key into |self.tt_dd|.
          tt_d: a tt dict.