langchain/retrievers/document_compressors/chain_extract.py/LLMChainExtractor/acompress_documents
class LLMChainExtractor:    async def acompress_documents(
        self, documents: Sequence[Document], query: str
    ) -> Sequence[Document]:
        """Compress page content of raw documents asynchronously."""
        outputs = await asyncio.gather(
            *[
                self.llm_chain.apredict_and_parse(**self.get_input(query, doc))
                for doc in documents
            ]
        )
        compressed_docs = []
        for i, doc in enumerate(documents):
            if len(outputs[i]) == 0:
                continue
            compressed_docs.append(
                Document(page_content=outputs[i], metadata=doc.metadata)
            )
        return compressed_docs