'Tags can be selectively cleared by namespace'

def test_clear_ns(self):

    apple = self.food_model.objects.create(name='apple')
    tags_cleared = ['a:1', 'a:2', 'a:3']
    tags_not_cleared = ['1', '2', 'b:1', 'b:2', 'c:1']
    apple.tags.add(*tags_cleared)
    apple.tags.add(*tags_not_cleared)
    apple.tags.clear_ns('a:')
    self.assert_tags_equal(apple.tags.all(), tags_not_cleared)
