presto-resource-group-managers/src/main/java/io/prestosql/plugin/resourcegroups/ResourceGroupIdTemplate.java/ResourceGroupIdTemplate/getVariableNames
class ResourceGroupIdTemplate:    public Set<String> getVariableNames()
    {
        return segments.stream()
                .flatMap(s -> s.getVariableNames().stream())
                .collect(toImmutableSet());
    }