How to use the spirit.core.tests.utils.cache_clear function in spirit

def setUp(self):
        utils.cache_clear()
        self.user = utils.create_user()
        self.category = utils.create_category()
        self.topic = utils.create_topic(category=self.category, user=self.user)
        self.comment = utils.create_comment(user=self.user, topic=self.topic)

def setUp(self):
        utils.cache_clear()
        self.user = utils.create_user()
        self.user2 = utils.create_user()
        self.category = utils.create_category()
        self.topic = utils.create_topic(self.category, user=self.user)
        self.topic2 = utils.create_topic(self.category, user=self.user2)
        self.comment = utils.create_comment(topic=self.topic)
        self.user_comment = utils.create_comment(topic=self.topic, user=self.user)
        self.poll = CommentPoll.objects.create(comment=self.comment, name='foo')
        self.poll_multi = CommentPoll.objects.create(comment=self.comment, name='bar', choice_max=2)

b'%PDF-1.0\n1 0 obj<>endobj 2 0 obj<>endobj 3 0 obj<>endobj\nxref\n0 4\n0000000000 65535 f\n000000'
            b'0010 00000 n\n0000000053 00000 n\n0000000102 00000 n\ntrailer<>\nstartxre'
            b'f\n149\n%EOF\n')
        file_name = 'foo.pdf'
        file = SimpleUploadedFile(
            file_name, pdf.read(), content_type='application/pdf')

        response = self.client.post(
            reverse('spirit:comment:file-upload-ajax'),
            HTTP_X_REQUESTED_WITH='XMLHttpRequest',
            data={'file': file})
        res = json.loads(response.content.decode('utf-8'))
        first_url = res['url']

        utils.cache_clear()
        file.seek(0)
        response = self.client.post(
            reverse('spirit:comment:file-upload-ajax'),
            HTTP_X_REQUESTED_WITH='XMLHttpRequest',
            data={'file': file})
        res = json.loads(response.content.decode('utf-8'))
        second_url = res['url']

        self.assertNotEqual(first_url, second_url)

def setUp(self):
        utils.cache_clear()
        self.user = utils.create_user()

def setUp(self):
        utils.cache_clear()
        self.user = utils.create_user()
        self.category = utils.create_category()
        self.topic = utils.create_topic(category=self.category, user=self.user)
        self.comment = utils.create_comment(topic=self.topic)

def setUp(self):
        utils.cache_clear()
        self.user = utils.create_user()
        self.category = utils.create_category()
        self.topic = utils.create_topic(self.category)
        self.comment = utils.create_comment(topic=self.topic)

        self.topic_notification = TopicNotification.objects.create(
            user=self.user, topic=self.topic,
            comment=self.comment, is_active=True,
            action=COMMENT)

def setUp(self):
        utils.cache_clear()

def setUp(self):
        utils.cache_clear()
        self.user = utils.create_user()
        self.category = utils.create_category()
        self.topic = utils.create_topic(self.category)

def setUp(self):
        utils.cache_clear()
        self.user = utils.create_user()
        self.category = utils.create_category()
        self.topic = utils.create_topic(category=self.category, user=self.user)
        self.topic2 = utils.create_topic(category=self.category, user=self.user)

        self.poll = TopicPoll.objects.create(topic=self.topic)
        self.poll_other = TopicPoll.objects.create(topic=self.topic2)

        self.poll_choice = TopicPollChoice.objects.create(poll=self.poll, description="op1")
        self.poll_choice2 = TopicPollChoice.objects.create(poll=self.poll, description="op2")
        self.poll_other_choice = TopicPollChoice.objects.create(poll=self.poll_other, description="op2")

        self.poll_vote = TopicPollVote.objects.create(user=self.user, choice=self.poll_choice)
        self.poll_other_vote = TopicPollVote.objects.create(user=self.user, choice=self.poll_other_choice)

"""
        Should prevent double posts
        """
        utils.login(self)
        category_private = Category.objects.get(
            pk=settings.ST_TOPIC_PRIVATE_CATEGORY_PK)
        topic_title = 'title foobar'

        # First post
        self.client.post(
            reverse('spirit:topic:private:publish'),
            {'comment': 'foo', 'title': topic_title, 'users': [self.user2.username]})
        self.assertEqual(len(Topic.objects.all()), 1)

        # Double post
        utils.cache_clear()  # Clear rate limit
        response = self.client.post(
            reverse('spirit:topic:private:publish'),
            {'comment': 'new foo', 'title': topic_title, 'users': [self.user2.username]})
        self.assertEqual(len(Topic.objects.all()), 1)  # Prevented!

        self.assertRedirects(
            response,
            expected_url=category_private.get_absolute_url(),
            status_code=302,
            target_status_code=200)

        # New post
        utils.cache_clear()  # Clear rate limit
        self.client.post(
            reverse('spirit:topic:private:publish'),
            {'comment': 'foo', 'title': 'new topic', 'users': [self.user2.username]})