code: def _run_player(self, extra_cmd):
          
          # Force quit old process
          if self.is_alive:
              self.quit()
          args = self._args + extra_cmd
          logger.debug("Exec: " + ' '.join(args))
          self.sub_proc = subprocess.Popen(
              args,
              stdin=subprocess.PIPE,
              stdout=subprocess.PIPE,
              stderr=self._null_file,
              preexec_fn=os.setsid
          )
          # Set up NONBLOCKING flag for the pipe
          flags = fcntl.fcntl(self.sub_proc.stdout, fcntl.F_GETFL)
          flags |= os.O_NONBLOCK
          fcntl.fcntl(self.sub_proc.stdout, fcntl.F_SETFL, flags)
          # Start watchdog
          Thread(target=self._watchdog).start()
docs: 运行播放器（若当前已有正在运行的，强制推出）
  
          extra_cmd: 额外的参数 (list)