def test_empty_collection_is_empty(self):
    c = Collection()
    c2 = Collection([])
    self.assertTrue(c.is_empty())
    self.assertTrue(c2.is_empty())
def test_empty_collection_is_empty(self):
    c = Collection()
    c2 = Collection([])
    self.assertTrue(c.is_empty())
    self.assertTrue(c2.is_empty())