@ConstantFunction(name = "weeks_sub", argTypes = {DATETIME, INT}, returnType = DATETIME, isMonotonic = true)
    public static ConstantOperator weeksSub(ConstantOperator date, ConstantOperator week) {
        return ConstantOperator.createDatetimeOrNull(date.getDatetime().minusWeeks(week.getInt()));
    }
@Test
    public void weeksSub() {
        assertEquals("2015-01-12T09:23:55",
                ScalarOperatorFunctions.weeksSub(O_DT_20150323_092355, O_INT_10).getDatetime().toString());
    }