def METHOD_NAME(
    self,
):
    input = InputCell(1)
    plus_one = ComputeCell(
        [
            input,
        ],
        lambda inputs: inputs[0] + 1,
    )
    minus_one = ComputeCell(
        [
            input,
        ],
        lambda inputs: inputs[0] - 1,
    )
    always_two = ComputeCell(
        [
            plus_one,
            minus_one,
        ],
        lambda inputs: inputs[0] - inputs[1],
    )
    cb1_observer = []
    callback1 = self.callback_factory(cb1_observer)
    always_two.add_callback(callback1)
    input.value = 2
    self.assertEqual(cb1_observer, [])
    input.value = 3
    self.assertEqual(cb1_observer, [])
    input.value = 4
    self.assertEqual(cb1_observer, [])
    input.value = 5
    self.assertEqual(cb1_observer, [])