presto-resource-group-managers/src/main/java/io/prestosql/plugin/resourcegroups/ResourceGroupNameTemplate.java/ResourceGroupNameTemplate/getVariableNames
class ResourceGroupNameTemplate:    public Set<String> getVariableNames()
    {
        return fragments.stream()
                .filter(NameFragment::isVariable)
                .map(NameFragment::getVariable)
                .collect(toImmutableSet());
    }