presto-main/src/main/java/io/prestosql/type/VarcharOperators.java/VarcharOperators/castToBinary
class VarcharOperators:    @LiteralParameters("x")
    @ScalarOperator(CAST)
    @SqlType(StandardTypes.VARBINARY)
    public static Slice castToBinary(@SqlType("varchar(x)") Slice slice)
    {
        return slice;
    }