Check if the given "value" (via `args`) is unique or not.

        For the parameters, see ``BaseIndex.check_uniqueness``

def check_uniqueness(self, *args, **kwargs):
        """Check if the given "value" (via `args`) is unique or not.

        For the parameters, see ``BaseIndex.check_uniqueness``

        """

        if not self.field.unique:
            return

        try:
            pk = self.instance.pk.get()
        except AttributeError:
            pk = None

        key = self.get_storage_key(*args)
        value = list(args)[-1]
        pks = self.get_pks_for_filter(key, 'eq', self.normalize_value(value))

        self.assert_pks_uniqueness(pks, pk, value)