'Tokenize multiple sentences using Repp.
:param sentences: A list of sentence strings.
:type sentences: list(str)
:return: A list of tuples of tokens
:rtype: iter(tuple(str))'

def tokenize_sents(self, sentences, keep_token_positions=False):

    with tempfile.NamedTemporaryFile(prefix=u'repp_input.', dir=self.working_dir, mode=u'w', delete=False) as input_file:
        for sent in sentences:
            input_file.write((text_type(sent) + u'\n'))
        input_file.close()
        cmd = self.generate_repp_command(input_file.name)
        repp_output = self._execute(cmd).decode(self.encoding).strip()
        for tokenized_sent in self.parse_repp_outputs(repp_output):
            if (not keep_token_positions):
                (tokenized_sent, starts, ends) = zip(*tokenized_sent)
            (yield tokenized_sent)
