docs: function keepAlive(k) {
  	if (k) {
  		if (++keepAliveIntervalCount === 1) {
  			// The actual duration doesn't really matter: it should be large but not too large.
  			keepAliveIntervalId = setInterval(() => { }, 24 * 60 * 60 * 1000);
  		}
  	} else {
  		if (--keepAliveIntervalCount === 0) {
  			clearInterval(keepAliveIntervalId);
  		}
  	}
  	debug(`keepAlive(${k}) => ${keepAliveIntervalCount}`);
  }