The PreAnswer element answers the incoming call in early media mode. This is useful when you want to play custom tunes or to use specified text dynamically while the call is still in an unanswered state.
You can nest Speak, Play, and Wait elements within the PreAnswer element. Learn more in the guide at the link: https://api-reference.plivo.com/latest/python/elements/preanswer
PreAnswer is not guaranteed to work for every destination. It’s not supported by every carrier due to regulations and abuse-prevention protocols. Therefore, there aren’t many steps you can take to increase the accuracy of the PreAnswer. Please note that the WebRTC SDK does not support early media (PreAnswer) as it's not a part of the WebRTC specifications.