return map.isEmpty();
    }

    /**
     * Returns true if this set contains the specified element.
     *
     * @param o
     *            element whose presence in this set is to be tested.
     * @return true if this set contains the specified element.
     */
    @Override
    public boolean contains(final Object o) {
        return map.containsKey(o);
    }

    /**

            if (quoted && query instanceof TermQuery termQuery) {
                final Pair<String, String> splitField = splitField(defaultField, field);
                if (defaultField.equals(splitField.cur)) {
                    final PhraseQuery.Builder builder = new PhraseQuery.Builder();
                    builder.add(termQuery.getTerm());
                    return builder.build();

                sb.append("]");
            }
            sb.append("; ");
            target = target.getCause();
            if (target != null) {
                sb.append("nested: ");
            }
        }
        return sb.toString();
    }

    protected void processLabelRequest(final HttpServletRequest request, final HttpServletResponse response, final FilterChain chain) {