async def start(self, sample_rate: int):
        """This will be called from the output transport when the transport is
        started. It can be used to initialize the mixer. The output transport
        sample rate is provided so the mixer can adjust to that sample rate.

        """
        pass
This will be called from the output transport when the transport is
        started. It can be used to initialize the mixer. The output transport
        sample rate is provided so the mixer can adjust to that sample rate.

        
src/pipecat/audio/mixers/base_audio_mixer.py