<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def stop(pid):
 """Shut down a specific process. Args: pid: the pid of the process to shutdown. """

    if psutil.pid_exists(pid):
      try:
        p = psutil.Process(pid)
        p.kill()
      except Exception:
        pass