langchain/vectorstores/base.py/VectorStore/_similarity_search_with_relevance_scores
class VectorStore:    def _similarity_search_with_relevance_scores(
        self,
        query: str,
        k: int = 4,
        **kwargs: Any,
    ) -> List[Tuple[Document, float]]:
        """Return docs and relevance scores, normalized on a scale from 0 to 1.

        0 is dissimilar, 1 is most similar.
        """
        raise NotImplementedError