if (fieldSet == null) {
            fieldSet = split(getIndexAdminArrayFields(), ",")
                    .get(stream -> stream.filter(StringUtil::isNotBlank).map(String::trim).collect(Collectors.toSet()));
            propMap.put(INDEX_ADMIN_ARRAY_FIELD_SET, fieldSet);
        }
        return fieldSet;
    }

    default boolean validateIndexArrayFields(final Map<String, Object> source) {

            servletContext.setSessionTrackingModes(
                    fessConfig.getSessionTrackingModesAsSet().stream().map(SessionTrackingMode::valueOf).collect(Collectors.toSet()));
        } catch (final Throwable t) {
            logger.warn("Failed to set SessionTrackingMode.", t);
        }

   * <p><b>Note:</b> if mutability is not required and the elements are non-null, use {@link
   * ImmutableSet#copyOf(Iterable)} instead. (Or, change {@code elements} to be a {@link
   * FluentIterable} and call {@code elements.toSet()}.)
   *
   * <p><b>Note:</b> if {@code E} is an {@link Enum} type, use {@link #newEnumSet(Iterable, Class)}
   * instead.
   *