@Override
  public void w(String tag, String msg, Throwable tr) {
    println(Log.WARN, tag, msg, tr);
  }
Sets an application tag that is used for checking if a log line is loggable and also to prefix
to all log lines.

@param tag the tag
fbcore/src/main/java/com/facebook/common/logging/FLogDefaultLoggingDelegate.java