presto-phoenix/src/main/java/io/prestosql/plugin/phoenix/PhoenixTableProperties.java/PhoenixTableProperties/getSplitOn
class PhoenixTableProperties:    public static Optional<String> getSplitOn(Map<String, Object> tableProperties)
    {
        requireNonNull(tableProperties);

        String value = (String) tableProperties.get(SPLIT_ON);
        if (value == null) {
            return Optional.empty();
        }

        return Optional.of(value);
    }