'Sending null in for a field \'deletes\' it'

def test_null_field(self):

    problem = self.get_item_from_modulestore(self.problem_usage_key, verify_is_draft=True)
    self.assertIsNotNone(problem.markdown)
    self.client.ajax_post(self.problem_update_url, data={'nullout': ['markdown']})
    problem = self.get_item_from_modulestore(self.problem_usage_key, verify_is_draft=True)
    self.assertIsNone(problem.markdown)
