langchain/document_loaders/web_base.py/WebBaseLoader/_fetch
class WebBaseLoader:    async def _fetch(
        self, url: str, retries: int = 3, cooldown: int = 2, backoff: float = 1.5
    ) -> str:
        async with aiohttp.ClientSession() as session:
            for i in range(retries):
                try:
                    async with session.get(
                        url, headers=self.session.headers
                    ) as response:
                        return await response.text()
                except aiohttp.ClientConnectionError as e:
                    if i == retries - 1:
                        raise
                    else:
                        logger.warning(
                            f"Error fetching {url} with attempt "
                            f"{i + 1}/{retries}: {e}. Retrying..."
                        )
                        await asyncio.sleep(cooldown * backoff**i)
        raise ValueError("retry count exceeded")