code: @SuppressWarnings("unchecked")
      protected final <K extends AbstractOption<?>, V extends AbstractOptionValue<K, ?>> Map<K, V> asMap0() {
          return Collections.unmodifiableMap((Map<? extends K, ? extends V>) valueMap);
      }
docs: Returns the {@link Map} whose key is {@link AbstractOption} and value is {@link AbstractOptionValue}.
  
  @param <K> the type of the options
  @param <V> the type of the option values