langchain/embeddings/openai.py/OpenAIEmbeddings/_embedding_func
class OpenAIEmbeddings:    def _embedding_func(self, text: str, *, engine: str) -> List[float]:
        """Call out to OpenAI's embedding endpoint."""
        # handle large input text
        if len(text) > self.embedding_ctx_length:
            return self._get_len_safe_embeddings([text], engine=engine)[0]
        else:
            if self.model.endswith("001"):
                # See: https://github.com/openai/openai-python/issues/418#issuecomment-1525939500
                # replace newlines, which can negatively affect performance.
                text = text.replace("\n", " ")
            return embed_with_retry(
                self,
                input=[text],
                engine=engine,
                request_timeout=self.request_timeout,
                headers=self.headers,
            )["data"][0]["embedding"]