'Take a sentence and return entities in json format'

def extract_entities(self, message):

    if (self.ent_tagger is not None):
        text_data = self._from_text_to_crf(message)
        features = self._sentence_to_features(text_data)
        ents = self.ent_tagger.predict_single(features)
        return self._from_crf_to_json(message, ents)
    else:
        return []
