Create a chain that takes conversation history and returns documents.
If there is no chat_history, then the input is just passed directly to the
retriever. If there is chat_history, then the prompt and LLM will be used
to generate a search query. That search query is then passed to the retriever.
An LCEL Runnable. The runnable input must take in input, and if there
is chat history should take it in the form of chat_history.
The Runnable output is a list of Documents
Create a chain that takes conversation history and returns documents. If there is no
chat_history, then theinputis just passed directly to the retriever. If there ischat_history, then the prompt and LLM will be used to generate a search query. That search query is then passed to the retriever.