langchain/vectorstores/base.py/VectorStore/asimilarity_search_by_vector
class VectorStore:    async def asimilarity_search_by_vector(
        self, embedding: List[float], k: int = 4, **kwargs: Any
    ) -> List[Document]:
        """Return docs most similar to embedding vector."""

        # This is a temporary workaround to make the similarity search
        # asynchronous. The proper solution is to make the similarity search
        # asynchronous in the vector store implementations.
        func = partial(self.similarity_search_by_vector, embedding, k, **kwargs)
        return await asyncio.get_event_loop().run_in_executor(None, func)