rdkafka: add PEP7 compliant docstrings
rdkafka: add PEP7 compliant docstrings

Also moves some object declarations to the top of the file, because
they're essentially like module imports.

Signed-off-by: Yung-Chin Oei <e4c1ab9da74060df152545062ee274845648ed6c@yungchin.nl>

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