def _serialize_occurrences(self, occurrences):
        return ', '.join(
            [':'.join([i for i in t ]) for t in occurrences]
        )
Serialize the occurrences list for saving to db.
dataset/ETHPy150Open rvanlaar/easy-transifex/src/transifex/transifex/resources/formats/pofile.py/GettextHandler._serialize_occurrences