':param fileids: A list specifying the fileids that should be used.
:return: the given file(s) as a list of words, the corresponding lemmas
and punctuation symbols, encoded as tuples (word, lemma)
:rtype: list(tuple(str,str))'

def lemma_words(self, fileids=None):

    return concat([MTEFileReader(os.path.join(self._root, f)).lemma_words() for f in self.__fileids(fileids)])
