Google Chat API / Webhook - how to post a message as a response to another message (With "Quote in Reply" option)?

Question

I use "threadKey=some-unique-key&messageReplyOption=REPLY_MESSAGE_FALLBACK_TO_NEW_THREAD" to respond to an existing thread (or start a new thread).

How do post a new message by quoting another message? The GUI has an option, but how do I do it thru Webhook?

My background - I use python to post messages thru webhook.

Google Chat GUI - "Quote in Reply" Option