Is there any method to override before chatInput bar is created?

When I subclassed PhotoMessageViewModel I could do some initial setup by
override func willBeShown() {
// Initial setup
}

Is there any other similar method which can be used for ChatInputBar, so as to do initial setup before default chatInputBar is created?

Start by tracing the lifecycle of PhotoMessageViewModel and the creation path for ChatInputBar, using the issue's willBeShown() example as the reference point. Determine whether an existing initialization hook is available; done means the supported setup point or required API change is clearly identified and covered by the relevant tests.

Written by the indexing model from the issue text.