How to stop bot command execution?

Question

Python

Hello, how do I make a bot command stop?
Let's say I write .. "! hello" and he starts writing hello every 3 seconds. And so on until you write the command "! stop" how to implement the stop command so that the hello command stops.

if text == "!привет":
    while True:
        vk.messages.send(peer_id=id,message=f"привет",random_id=0)