langchain/vectorstores/mongodb_atlas.py/MongoDBAtlasVectorSearch/similarity_search
class MongoDBAtlasVectorSearch:    def similarity_search(
        self,
        query: str,
        k: int = 4,
        pre_filter: Optional[dict] = None,
        post_filter_pipeline: Optional[List[Dict]] = None,
        **kwargs: Any,
    ) -> List[Document]:
        """Return MongoDB documents most similar to query.

        Use the knnBeta Operator available in MongoDB Atlas Search
        This feature is in early access and available only for evaluation purposes, to
        validate functionality, and to gather feedback from a small closed group of
        early access users. It is not recommended for production deployments as we may
        introduce breaking changes.
        For more: https://www.mongodb.com/docs/atlas/atlas-search/knn-beta

        Args:
            query: Text to look up documents similar to.
            k: Optional Number of Documents to return. Defaults to 4.
            pre_filter: Optional Dictionary of argument(s) to prefilter on document
                fields.
            post_filter_pipeline: Optional Pipeline of MongoDB aggregation stages
                following the knnBeta search.

        Returns:
            List of Documents most similar to the query and score for each
        """
        docs_and_scores = self.similarity_search_with_score(
            query,
            k=k,
            pre_filter=pre_filter,
            post_filter_pipeline=post_filter_pipeline,
        )
        return [doc for doc, _ in docs_and_scores]