I want to stream from Twitter firehose using Tweepy but I'm not sure if stream.sample(async=False) would work in firehose mode or it is just designed for sampling 1% of the stream?
If it doesn't work for firehose how should one stream firehose using Tweepy?
No it doesn't. For firehose stream.firehose() should be called. For samples stream.sample() should be called. Note that for firehose to work, it is needed for the user to have authorization to the firehose data.