From the code, seems "fast" table_strategy would only return None instead of table content, is this somewhat unreasonable?

It appears "hq" strategy uses unstructured pkg to extract table, I also used this pkg, and find it actually performed worse than table-transformer.

Also does the "llm" strategy return the reliable table contents? From the code, looks like it uses LLM and a prompt to generate the table summarization of the document, but from my previous experience, such way would generate results that significantly deviate the table content sometimes.

Thanks for insightful comments, my opinion on these issues are as follows:

From the code, seems "fast" table_strategy would only return None instead of table content, is this somewhat unreasonable?

In fact, by default, our program will use OCR to extract all text information in files including table information, which has been implemented in other PRs. This PR is just to further enhance the understanding of the table, so no content is returned in fast mode (fast mode is also the default mode).

It appears "hq" strategy uses unstructured pkg to extract table, I also used this pkg, and find it actually performed worse than table-transformer.

At present, we do use unstructured to extract table information, and the extraction performance is quite satisfactory. We have not tried the table transformer, but it is indeed worth considering.

Also does the "llm" strategy return the reliable table contents? From the code, looks like it uses LLM and a prompt to generate the table summarization of the document, but from my previous experience, such way would generate results that significantly deviate the table content sometimes.

Your understanding of what llm mode does is correct. It is true that llm's table summary is not completely reliable, but according to the experimental results, there will be much better table QA performance in llm mode overall.