Bloodtype holder class

class GeneralHolder:
    def __init__(self, node, textname):
        self.node = node
        self.textname = textname
        self.value = node.findtext(textname)

    def __eq__(self, other):
        return self.__value.upper() == other.upper()

    @property
    def value(self):
        return self.__value

    @value.setter
    def value(self, v):
        self.__value = v
        self.node.find(self.textname).text = v

    def like(self, ls):
        return ls.upper() in self.__value.upper()


class BtHolder(GeneralHolder):
    BLOODTYPES = {"O", "A", "B", "A1", "A1B", "non-A1", "non-A1B", "AB"}

    #def __eq__(self, other):
    #    return self.__value.upper() == other.upper()

    @property
    def value(self):
        return self.__value

    @value.setter
    def value(self, v):
        if v not in self.BLOODTYPES:
            raise AttributeError("bad bloodtype value: " + v + ", candidates are: " + str(sorted(self.BLOODTYPES)))
        self.__value = v
        self.node.find(self.textname).text = v