presto-main/src/main/java/io/prestosql/operator/scalar/StringFunctions.java/StringFunctions/toUtf8
class StringFunctions:    @Description("encodes the string to UTF-8")
    @ScalarFunction
    @LiteralParameters("x")
    @SqlType(StandardTypes.VARBINARY)
    public static Slice toUtf8(@SqlType("varchar(x)") Slice slice)
    {
        return slice;
    }