def test_forget(self):
    c = Collection(['foo', 'bar', 'boom'])
    c.forget(0)
    self.assertEqual('bar', c[0])
    c.forget(0, 1)
    self.assertTrue(c.is_empty())
def test_forget(self):
    c = Collection(['foo', 'bar', 'boom'])
    c.forget(0)
    self.assertEqual('bar', c[0])
    c.forget(0, 1)
    self.assertTrue(c.is_empty())