def METHOD_NAME(self) -> None:
    formatted_inputs = (
        torch.tensor([[0.0, 0.0], [0.0, 0.0]]),
        torch.tensor([]),  # empty tensor
        torch.tensor([[0.0, 0.0, 0.0], [0.0, 0.0, 0.0]]),
    )
    expected_mask = (
        torch.tensor([[0, 1]]),
        torch.tensor([]),
        torch.tensor([[2, 3, 4]]),
    )
    formatted_none_mask = _format_feature_mask(None, formatted_inputs)
    self.assertEqual(type(formatted_none_mask), tuple)
    assertTensorTuplesAlmostEqual(self, formatted_none_mask, expected_mask)