langchain/chains/qa_with_sources/retrieval.py/RetrievalQAWithSourcesChain/_get_docs
class RetrievalQAWithSourcesChain:    def _get_docs(self, inputs: Dict[str, Any]) -> List[Document]:
        question = inputs[self.question_key]
        docs = self.retriever.get_relevant_documents(question)
        return self._reduce_tokens_below_limit(docs)