'load the wordnet data of the requested language from the file to
the cache, _lang_data'

def _load_lang_data(self, lang):

    if (lang in self._lang_data.keys()):
        return
    if (lang not in self.langs()):
        raise WordNetError(u'Language    is    not    supported.')
    f = self._omw_reader.open(u'{0:}/wn-data-{0:}.tab'.format(lang))
    self.custom_lemmas(f, lang)
    f.close()
