code: public String alias(Object cls, String defaultValue) {
          assertArgumentNotNull("defaultValue", defaultValue);
          if (cls != null) {
              return alias(cls);
          } else {
              return defaultValue;
          }
      }
docs: Get classification alias or default value if the classification is null.
  @param cls The instance of classification to get code. (NotNull)
  @param defaultValue The default value for no classification. (NotNull, EmptyAllowed)
  @return The alias of classification. (NotNull: if not classification, throws exception)