Update and existing message

I’m trying to modify the text content of an existing message using the ‘OpenAI’.beta.threads.messages.update method. I’ve been unable to find a clear example of how to provide the call parameters (other than message_id and thread_id).
My questions are:

  1. Can I update an existing message, including one provided in an earlier query by the assistant?
  2. What is the proper way to call the method and what parameters (or json) does it accept.