langchain/retrievers/document_compressors/chain_extract.py/LLMChainExtractor/compress_documents
class LLMChainExtractor:    def compress_documents(
        self, documents: Sequence[Document], query: str
    ) -> Sequence[Document]:
        """Compress page content of raw documents."""
        compressed_docs = []
        for doc in documents:
            _input = self.get_input(query, doc)
            output = self.llm_chain.predict_and_parse(**_input)
            if len(output) == 0:
                continue
            compressed_docs.append(Document(page_content=output, metadata=doc.metadata))
        return compressed_docs