Django UnitTest with Mock

I am writing an Unit-Test for a Django class-based view.

class ExampleView(ListView):

     def get_context_data(self, **kwargs):
         context = super(EampleView, self).get_context_data(**kwargs)
         ## do something else

     def get_queryset(self, **kwargs):
         return self.get_data()

     def get_data(self):
         call_external_API()
         ## do something else

The key issue is that call_external_API() in get_data().

When I am writing Unit-test, I don't really want to call external API to get data. First, that will cost my money; second, I can easily test that API in another test file.

I also can easily test this get_data() method by having an unit-test only for it and mock the output of call_external_API().

However, when I test this whole class-based view, I simple will do

self.client.post('/example/url/')

and check the status code and context data to verify it.

In this case, how do I mock this call_external_API() when I am testing the whole class-based view?