def test_form_valid_updates_session(self):
        session = self.client.session
        self.assertNotIn('impersonate_id', session)
        self.client.post(
            reverse('become_user', kwargs={'user_uuid': self.normal_user.uuid}),
            {'user_to_become': self.normal_user.pk}
        )
        session = self.client.session
        self.assertEqual(session['impersonate_id'], self.normal_user.pk)
form_valid should add impersonate_id to the session.
dataset/ETHPy150Open ofa/connect/open_connect/accounts/tests/test_views.py/BecomeUserViewTest.test_form_valid_updates_session