optimizer: torch.optim.optimizer.Optimizer,
    cool_down: int,
    warm_up: int,
    ratio: int = 10,
    last_epoch: int = -1,
) -> None

Adjust momentum during training according to an inverted triangle-like schedule.

The momentum starts off high, then decreases linearly for cool_down epochs, until reaching 1 / ratio th of the original value. Then the momentum increases linearly for warm_up epochs until reaching its original value again. If there are still more epochs left over to train, the momentum will stay flat at the original value.

Registered as a MomentumScheduler with name "inverted_triangular".