presto-main/src/main/java/io/prestosql/operator/scalar/StringFunctions.java/StringFunctions/normalize
class StringFunctions:    @Description("transforms the string to normalized form")
    @ScalarFunction
    @LiteralParameters({"x", "y"})
    @SqlType(StandardTypes.VARCHAR)
    public static Slice normalize(@SqlType("varchar(x)") Slice slice, @SqlType("varchar(y)") Slice form)
    {
        Normalizer.Form targetForm;
        try {
            targetForm = Normalizer.Form.valueOf(form.toStringUtf8());
        }
        catch (IllegalArgumentException e) {
            throw new PrestoException(INVALID_FUNCTION_ARGUMENT, "Normalization form must be one of [NFD, NFC, NFKD, NFKC]");
        }
        return utf8Slice(Normalizer.normalize(slice.toStringUtf8(), targetForm));
    }