async def mix(self, audio: bytes) -> bytes:
        """This is called with the audio that is about to be sent from the
        output transport and that should be mixed with the mixer audio if the
        mixer is enabled.

        """
        pass
This is called with the audio that is about to be sent from the
        output transport and that should be mixed with the mixer audio if the
        mixer is enabled.

        
src/pipecat/audio/mixers/base_audio_mixer.py