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

def lemma_sents(self, fileids=None):

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