presto-accumulo/src/main/java/io/prestosql/plugin/accumulo/AccumuloClient.java/AccumuloClient/getColumnLocalityGroup
class AccumuloClient:    private static Optional<String> getColumnLocalityGroup(String columnName, Optional<Map<String, Set<String>>> groups)
    {
        if (groups.isPresent()) {
            for (Map.Entry<String, Set<String>> group : groups.get().entrySet()) {
                if (group.getValue().contains(columnName.toLowerCase(Locale.ENGLISH))) {
                    return Optional.of(group.getKey());
                }
            }
        }

        return Optional.empty();
    }