def clear_dns_cache(
        self, host: Optional[str] = None, port: Optional[int] = None
    ) -> None:
        """Remove specified host/port or clear all dns local cache."""
        if host is not None and port is not None:
            self._cached_hosts.remove((host, port))
        elif host is not None or port is not None:
            raise ValueError("either both host and port " "or none of them are allowed")
        else:
            self._cached_hosts.clear()
Remove specified host/port or clear all dns local cache.
lib/aiohttp/connector.py