code: public static Fetch convert(
        AttributeFilter attrFilter, EntityType entityType, String languageCode) {
      if (attrFilter == null || attrFilter.isStar()) {
        return createDefaultEntityFetch(entityType, languageCode);
      }
  
      Fetch fetch = new Fetch();
      createFetchContentRec(attrFilter, entityType, fetch, languageCode);
      return fetch;
    }
docs: Converts {@link AttributeFilter} to {@link Fetch} based on {@link EntityType}.
  
  @param attrFilter the {@link AttributeFilter} to convert
  @param entityType {@link EntityType} for the entity
  @return {@link Fetch}, or null for 'all attributes' {@link AttributeFilter} there are no
  refEntities
  @throws UnknownAttributeException if the entity does not have one of the attributes mentioned
  in the filter