How to obtain the source text from the response of file search

Hi,

I am using openai file search tool for RAG application. The response was like “It is a rainy season 【5:2†source】”. I am trying to get the source text (i.e., trunk in RAG) of the file I uploaded to openai file search. I can get the file id by message_content.annotations[0].file_citation.file_id, which is for example “file-123456789”, but I don’t see a way to further fetch the source text for this answer. Any help would be greatly appreciated!