code: private void checkForValid(String paramName, Attribute<? super X, ?> attribute)
      {
          if (attribute == null)
          {
              throw new IllegalArgumentException(
                      "attribute of the given name and type is not present in the managed type, for name:" + paramName);
  
          }
      }
docs: Check for valid.
  
  @param paramName
  the param name
  @param attribute
  the attribute