@Override
    public Set<UUID> getUniqueUsers() throws IOException {
        return this.users.getNode().getChildrenMap().keySet().stream()
                .map(Object::toString)
                .map(Uuids::fromString)
                .filter(Objects::nonNull)
                .collect(Collectors.toSet());
    }
Flat-file storage using Configurate {@link ConfigurationNode}s.
The data for users/groups/tracks is stored in a single shared file.
common/src/main/java/me/lucko/luckperms/common/storage/implementation/file/CombinedConfigurateStorage.java