*/
  public static <K extends @Nullable Object, V extends @Nullable Object>
      MapDifference<K, V> difference(
          Map<? extends K, ? extends V> left, Map<? extends K, ? extends V> right) {
    if (left instanceof SortedMap) {
      @SuppressWarnings("unchecked")
      SortedMap<K, ? extends V> sortedLeft = (SortedMap<K, ? extends V>) left;
      return difference(sortedLeft, right);
    }

    }

    protected <ENTITY extends AccessToken> ENTITY doSelectByPK(String id, Class<? extends ENTITY> tp) {
        return doSelectEntity(xprepareCBAsPK(id), tp);
    }

    protected AccessTokenCB xprepareCBAsPK(String id) {
        assertObjectNotNull("id", id);
        return newConditionBean().acceptPK(id);
    }

    }

    protected <ENTITY extends ElevateWordToLabel> ENTITY doSelectByPK(String id, Class<? extends ENTITY> tp) {
        return doSelectEntity(xprepareCBAsPK(id), tp);
    }

    protected ElevateWordToLabelCB xprepareCBAsPK(String id) {
        assertObjectNotNull("id", id);
        return newConditionBean().acceptPK(id);
    }

    }

    protected <ENTITY extends KeyMatch> ENTITY doSelectByPK(String id, Class<? extends ENTITY> tp) {
        return doSelectEntity(xprepareCBAsPK(id), tp);
    }

    protected KeyMatchCB xprepareCBAsPK(String id) {
        assertObjectNotNull("id", id);
        return newConditionBean().acceptPK(id);
    }

    }

    protected <ENTITY extends RelatedContent> ENTITY doSelectByPK(String id, Class<? extends ENTITY> tp) {
        return doSelectEntity(xprepareCBAsPK(id), tp);
    }

    protected RelatedContentCB xprepareCBAsPK(String id) {
        assertObjectNotNull("id", id);
        return newConditionBean().acceptPK(id);
    }

    }

    protected <ENTITY extends RelatedQuery> ENTITY doSelectByPK(String id, Class<? extends ENTITY> tp) {
        return doSelectEntity(xprepareCBAsPK(id), tp);
    }

    protected RelatedQueryCB xprepareCBAsPK(String id) {
        assertObjectNotNull("id", id);
        return newConditionBean().acceptPK(id);
    }

    }

    protected <ENTITY extends FavoriteLog> ENTITY doSelectByPK(String id, Class<? extends ENTITY> tp) {
        return doSelectEntity(xprepareCBAsPK(id), tp);
    }

    protected FavoriteLogCB xprepareCBAsPK(String id) {
        assertObjectNotNull("id", id);
        return newConditionBean().acceptPK(id);
    }

    }

    protected <ENTITY extends Group> ENTITY doSelectByPK(String id, Class<? extends ENTITY> tp) {
        return doSelectEntity(xprepareCBAsPK(id), tp);
    }

    protected GroupCB xprepareCBAsPK(String id) {
        assertObjectNotNull("id", id);
        return newConditionBean().acceptPK(id);
    }

     * @return an OptionalEntity containing the dictionary file if found, empty otherwise
     */
    public OptionalEntity<DictionaryFile<? extends DictionaryItem>> getDictionaryFile(final String id) {
        for (final DictionaryFile<? extends DictionaryItem> dictFile : getDictionaryFiles()) {
            if (dictFile.getId().equals(id)) {
                return OptionalEntity.of(dictFile);
            }
        }

    }

    protected <ENTITY extends CrawlingInfoParam> ENTITY doSelectByPK(String id, Class<? extends ENTITY> tp) {
        return doSelectEntity(xprepareCBAsPK(id), tp);
    }

    protected CrawlingInfoParamCB xprepareCBAsPK(String id) {
        assertObjectNotNull("id", id);
        return newConditionBean().acceptPK(id);
    }