Comparaison function. Can be used to sort labels alphabetically.

def __label_cmp(self, other):
        """
        Comparaison function. Can be used to sort labels alphabetically.
        """
        if other is None:
            return -1

        label_name = strip_accents(self.name).lower()
        other_name = strip_accents(other.name).lower()
        if label_name < other_name:
            return -1
        elif label_name == other_name:
            return 0
        else:
            return 1

        if self.get_color_str() < other.get_color_str():
            return -1
        elif self.get_color_str() == other.get_color_str():
            return 0
        else:
            return 1