code: public static <U> U valueOrElse(Versioned<U> versioned, U defaultValue) {
      return versioned == null ? defaultValue : versioned.value();
    }
docs: Returns the value of the specified Versioned object if non-null or else returns
  a default value.
  
  @param versioned    versioned object
  @param defaultValue default value to return if versioned object is null
  @param <U>          type of the versioned value
  @return versioned value or default value if versioned object is null