@staticmethod
def test_sum() -> None:
    d = (Binomial() + Binomial())
    assert (d.expectation() == 0)
    assert (d.variance() == 0)
    assert (d.pmf == {})
@staticmethod
def test_sum() -> None:
    d = (Binomial() + Binomial())
    assert (d.expectation() == 0)
    assert (d.variance() == 0)
    assert (d.pmf == {})