def test_pull(self):
    c = Collection([1, 2, 3, 4])
    c.pull(2)
    self.assertEqual([1, 2, 4], c.all())
def test_pull(self):
    c = Collection([1, 2, 3, 4])
    c.pull(2)
    self.assertEqual([1, 2, 4], c.all())