static LevelFiller parseLevelParameter(String wrappedParameter, String trimmedParameter) {
    if (trimmedParameter.equals(PARAMETER_LEVEL_SHORT)) {
      return new LevelFiller(wrappedParameter, trimmedParameter, false);
    } else if (trimmedParameter.equals(PARAMETER_LEVEL_LONG)) {
      return new LevelFiller(wrappedParameter, trimmedParameter, true);
    }
    return null;
  }
Try to create a level filler if the given parameter is a level parameter.

@return created level filler, or null if the given parameter is not a level parameter
xlog/src/main/java/com/elvishew/xlog/flattener/PatternFlattener.java