def data_section(self, tokens, labeled=None):
        """
        Returns the ARFF data section for the given data.

        :param tokens: a list of featuresets (dicts) or labelled featuresets
            which are tuples (featureset, label).
        :param labeled: Indicates whether the given tokens are labeled
            or not.  If None, then the tokens will be assumed to be
            labeled if the first token's value is a tuple or list.
        """
        # Check if the tokens are labeled or unlabeled.  If unlabeled,
        # then use 'None'
        if labeled is None:
            labeled = tokens and isinstance(tokens[0], (tuple, list))
        if not labeled:
            tokens = [(tok, None) for tok in tokens]

        # Data section
        s = '\n@DATA\n'
        for (tok, label) in tokens:
            for fname, ftype in self._features:
                s += '%s,' % self._fmt_arff_val(tok.get(fname))
            s += self._fmt_arff_val(label) % '%s\n'

        return s
dataset/ETHPy150Open nltk/nltk/nltk/classify/weka.py/ARFF_Formatter.data_section/swapped operands of `%`