langchain/retrievers/document_compressors/base.py/DocumentCompressorPipeline/compress_documents
class DocumentCompressorPipeline:    def compress_documents(
        self, documents: Sequence[Document], query: str
    ) -> Sequence[Document]:
        """Transform a list of documents."""
        for _transformer in self.transformers:
            if isinstance(_transformer, BaseDocumentCompressor):
                documents = _transformer.compress_documents(documents, query)
            elif isinstance(_transformer, BaseDocumentTransformer):
                documents = _transformer.transform_documents(documents)
            else:
                raise ValueError(f"Got unexpected transformer type: {_transformer}")
        return documents