public Set<String> getSavedCollections() {
        if (!Files.exists(this.container)) {
            return ImmutableSet.of();
        }

        try (Stream<Path> s = Files.list(this.container)) {
            return s.filter(Files::isDirectory)
                    .map(p -> p.getFileName().toString())
                    .collect(ImmutableCollectors.toSet());
        } catch (IOException e) {
            e.printStackTrace();
            return ImmutableSet.of();
        }
    }
Returns a set of all known collections

@return the identifiers of all known collections
sponge/src/main/java/me/lucko/luckperms/sponge/service/model/persisted/SubjectStorage.java