code: public void addIndividual(String className, ClassInformation classInformation) {
          Validate.notNull(className);
          Validate.notNull(classInformation);
          Validate.isTrue(!hierarchyMap.containsKey(className));
          
          hierarchyMap.put(className, classInformation);
      }
docs: Add a custom class.
  @param className name of class
  @param classInformation information for class
  @throws NullPointerException if any argument is {@code null}
  @throws IllegalArgumentException if {@code className} already exists in this repository