docstring note about strong references to Topics. fixes #427
docstring note about strong references to Topics. fixes #427

thedrow/samsa,wikimedia/operations-debs-python-pykafka,benauthor/pykafka,benauthor/pykafka,thedrow/samsa,wikimedia/operations-debs-python-pykafka,thedrow/samsa,wikimedia/operations-debs-python-pykafka,benauthor/pykafka