Learning rate scheduling

scheduler = optim.X(optimizer,...)      # create lr scheduler
scheduler.step()                        # update lr after optimizer updates weights
optim.lr_scheduler.X                    # where X is LambdaLR, MultiplicativeLR,
                                        # StepLR, MultiStepLR, ExponentialLR,
                                        # CosineAnnealingLR, ReduceLROnPlateau, CyclicLR,
                                        # OneCycleLR, CosineAnnealingWarmRestarts,