def _select_relevance_score_fn(self) -> Callable[[float], float]:
        """
        The 'correct' relevance function
        may differ depending on a few things, including:
        - the distance / similarity metric used by the VectorStore
        - the scale of your embeddings (OpenAI's are unit normed. Many others are not!)
        - embedding dimensionality
        - etc.
        """
        if self.override_relevance_score_fn is not None:
            return self.override_relevance_score_fn
        # Default strategy is to rely on distance strategy provided
        # in vectorstore constructor
        if self._distance_strategy == DistanceStrategy.COSINE:
            return lambda x: x
        elif self._distance_strategy == DistanceStrategy.EUCLIDEAN_DISTANCE:
            return lambda x: x
        else:
            raise ValueError(
                "No supported normalization function"
                f" for distance_strategy of {self._distance_strategy}."
                "Consider providing relevance_score_fn to PGVector constructor."
            )