def METHOD_NAME(self, data, tags):
    if "ref:vatin" in tags:
        if tags["ref:vatin"].startswith("IT"):
            if self.it_vatin(tags["ref:vatin"][2:]) is False:
                return {"class": 32601, "subclass": 1, "text": T_(u"Invalid 'VAT identification number'")}
        else:
            if len(tags["ref:vatin"]) < 3:
                return {"class": 32601, "subclass": 0, "text": T_(u"Value too short")}
            if tags["ref:vatin"][0:2].isalpha() is False:
                return {"class": 32601, "subclass": 2, "text": T_(u"Country code is missing")}
            if tags["ref:vatin"].isupper() is False:
                return {"class": 32601, "subclass": 3, "text": T_(u"Value is not uppercase")}