RetrieveUserProxyAgent in a nested group chat

[yabli]

Hi, could anyone help shed light or help point example how do I implement a group chat with one RetrieveUserProxyAgent and one RetrieveAssistantAgent, and use it as a nested group chat?

mini chart to explain my agents:
user_proxy -> user_assistant ->
-> group_chat[runbook_proxy(this is the RetrieveUserProxyAgent) -> runbook_assistant(RetrieveAssistantAgent)]

in my test, runbook_proxy never loads the giving documents, it also does not call runbook_assistant. Will be great if any recommendations I can re-wire the agents to make it reply to user_assistant agent in RAG way.

Thanks a lot