def startProducing(consumer):
        """
        Start producing to the given
        L{IConsumer<twisted.internet.interfaces.IConsumer>} provider.

        @return: A L{Deferred<twisted.internet.defer.Deferred>} which fires with
            L{None} when all bytes have been produced or with a
            L{Failure<twisted.python.failure.Failure>} if there is any problem
            before all bytes have been produced.
        """

        Start producing to the given
        L{IConsumer<twisted.internet.interfaces.IConsumer>} provider.

        @return: A L{Deferred<twisted.internet.defer.Deferred>} which fires with
            L{None} when all bytes have been produced or with a
            L{Failure<twisted.python.failure.Failure>} if there is any problem
            before all bytes have been produced.
        
stackoverflow/venv/lib/python3.6/site-packages/twisted/web/iweb.py