def test_derivative(self):
a = Sigmoid()
self.assertEqual(a.derivative(1),
1 / (1 + np.exp(-1)) * (1 - 1 / (1 + np.exp(-1))))
self.assertEqual(
a.derivative(10000),
1 / (1 + np.exp(-10000)) * (1 - 1 / (1 + np.exp(-10000))))
self.assertEqual(
a.derivative(-10000),
1 / (1 + np.exp(10000)) * (1 - 1 / (1 + np.exp(10000))))
