public static void w(String msg, Throwable tr) {
    assertInitialization();
    sLogger.w(msg, tr);
  }
public static void w ( String msg , Throwable tr ) { assertInitialization ( ) ; sLogger . w ( msg , tr ) ; }
Log a message and a throwable with level {@link LogLevel#WARN}.

@param msg the message to log
@param tr  the throwable to be log