CycleGAN notebook is broken with updated ParamGroupScheduler

[vfdev-5]

ignite/ignite/contrib/handlers/param_scheduler.py

Line 960 in c2c4a36

raise ValueError("schedulers should be related to same optimizer")

@sdesrozis above code brakes our cycle gan notebook where we do

gen_lr_scheduler = PiecewiseLinear(optimizer_D, param_name='lr', milestones_values=milestones_values)
desc_lr_scheduler = PiecewiseLinear(optimizer_G, param_name='lr', milestones_values=milestones_values)

lr_scheduler = ParamGroupScheduler([gen_lr_scheduler, desc_lr_scheduler], 
                                   names=['gen_lr_scheduler', 'desc_lr_scheduler'])

Can we simply remove that check ?

[sdesrozis]

Ok, I didn't add this usecase in mind.

It need more fixes than simply remove the test

ignite/ignite/contrib/handlers/param_scheduler.py

Line 1047 in c2c4a36

objs["optimizer"] = schedulers[0].optimizer.state_dict()

I do it and I add a test

[vfdev-5]

Thanks, Sylvain !