return a prediction of label names

def guess_labels(self, doc):
        """
        return a prediction of label names
        """
        if doc.nb_pages <= 0:
            return set()
        self.label_guesser.total_nb_documents = len(self._docs_by_id.keys())
        label_names = self.label_guesser.guess(doc)
        labels = set()
        for label_name in label_names:
            label = self.labels[label_name]
            labels.add(label)
        return labels