* and ** example

class D:
    contents = ['a', 'b', 'c']
    def __getitem__(self, x):
        return self.contents[x]
    def __contains__(self, key):
        return key in self.keys()
    def keys(self):
        return range(len(self.contents))


assert {**D()} == {0: 'a', 1: 'b', 2: 'c'}
assert [*D()] == ['a', 'b', 'c']