presto-main/src/main/java/io/prestosql/operator/scalar/FormatFunction.java/FormatFunction/converter
class FormatFunction:    private static BiFunction<ConnectorSession, Block, Object> converter(Metadata metadata, Type type, int position)
    {
        BiFunction<ConnectorSession, Block, Object> converter = valueConverter(metadata, type, position);
        return (session, block) -> block.isNull(position) ? null : converter.apply(session, block);
    }