I need to write a unit test case for my Django server, where I have the structure like following code snippet. This is just a pseudo-code because I just want to get the idea about the approach.
# views.py
class UserView(ViewSet):
    def get_info_from_multiple_sources(self, request):
        # assume url for this action is /users/:id/info
        user_id = get_parameters(request)
        info = info_service.get_info(user_id)
        return Response(info)
# user_info_service.py
class UserInfoService:
    def get_info(user_id):
        user_fb_info = fb_service.get_user_info(user_id)
        user_twitter_info = twitter_service.get_user_info(user_id)
        merged_info = merge_info(user_fb_info, user_twitter_info)
        return merged_info
# fb_service.py
class FbService:
    def _manipulate_data(response):
        user_info = None
        # do some processing here, to convert data from fb format to 
        # project format. Assign formatted response to user_info variable.
        return user_info
    def get_user_info(user_id):
        # lets say this imaginary urls gives user info somehow magically.
        response = requests.request('http://fb.com/users/{0}'.format(user_id))
        return self._manipulate_data(response)
# twitter_Service.py
class TwitterService:
    def _manipulate_data(response):
        user_info = None
        # do some processing here, to convert data from twitter format to 
        # project format. Assign formatted response to user_info variable.
        return user_info
    def get_user_info(user_id):
        response  = requests.request('http://twitter.com/users/{0}'.format(user_id))
        return self._manipulate_data(response)
# test_user_info_endpoint.py
class TestUserInfoViewEndpoint(APITestCase):
    def test_user_info(self):
        # how to write a unit test function where
        # I will be mocking only requests.request call. i.e outgoing call to external APIs
I am using unittests framework, and I am open to using any standard library for it.