Django: mock function that is called by other function

Imagine that there is a models.py file which have update and bulk_update methods

...
@staticmethod
def bulk_update(self, ids):
  for id in ids:
    Foo.objects.get(id=id).update()

def update(self):
  pass
...

Not imagine that we have tests.py file, where we want to mock the update method. The problem is that whatever I do, mock_update always calls original update instead of a mocked one.

TRY #1:

# NOT WORKING
@mock.patch('models.Foo.update')
class FooTestCase(TestCase):
  def test_foo(self):
    Foo.bulk_update([1,2,3])