langchain/retrievers/document_compressors/embeddings_filter.py/EmbeddingsFilter/compress_documents
class EmbeddingsFilter:    def compress_documents(
        self, documents: Sequence[Document], query: str
    ) -> Sequence[Document]:
        """Filter documents based on similarity of their embeddings to the query."""
        stateful_documents = get_stateful_documents(documents)
        embedded_documents = _get_embeddings_from_stateful_docs(
            self.embeddings, stateful_documents
        )
        embedded_query = self.embeddings.embed_query(query)
        similarity = self.similarity_fn([embedded_query], embedded_documents)[0]
        included_idxs = np.arange(len(embedded_documents))
        if self.k is not None:
            included_idxs = np.argsort(similarity)[::-1][: self.k]
        if self.similarity_threshold is not None:
            similar_enough = np.where(
                similarity[included_idxs] > self.similarity_threshold
            )
            included_idxs = included_idxs[similar_enough]
        return [stateful_documents[i] for i in included_idxs]