Load a tt dict into |self.tt_dd|.
        |tt| means text transform.
        
        locale: key into |self.tt_dd|.
        tt_d: a tt dict.

def load_tt_dict(self, locale, tt_d):
        """
        Load a tt dict into |self.tt_dd|.
        |tt| means text transform.
        
        locale: key into |self.tt_dd|.
        tt_d: a tt dict.
        """
        
        #/ 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)