How to enable TCP keepalive feature?

In `urllib3` docs, there're ways to add tcp keepalive options to `HTTPConnection`
```
HTTPConnection.default_socket_options + [
    (socket.SOL_SOCKET, socket.SO_KEEPALIVE, 1),
]
```

but on `httpx` or `httpcore`, I didn't find the way to do same thing, any solutions if I want to enable tcp keepalive?