async def METHOD_NAME(
    self,
    inputs: Dict[str, Any],
    run_manager: Optional[AsyncCallbackManagerForChainRun] = None,
) -> Dict[str, Any]:
    """Run _get_docs on input query.
    Returns the retrieved documents under the key 'source_documents'.
    Example:
    .. code-block:: python
    chain = _RetrieverChain(retriever=...)
    res = chain({'query': 'This is my query'})
    docs = res['source_documents']
    """
    question = inputs[self.input_key]
    docs = await self._aget_docs(question)
    list_of_str_page_content = [doc.page_content for doc in docs]
    return {self.output_key: json.dumps(list_of_str_page_content)}