<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def chat(ws):
 """Relay chat messages to and from clients. """

    lag_tolerance_secs = float(request.args.get("tolerance", 0.1))
    client = Client(ws, lag_tolerance_secs=lag_tolerance_secs)
    client.subscribe(request.args.get("channel"))
    gevent.spawn(client.heartbeat)
    client.publish()