FedAvgM expecting initial_parameters as Optional about flower

[DanielCardeal]

As far as I can tell, initial_parameters are required when using server side optimization in the FedAvgM strategy, as indicated by this if statement above the assertion clause.

Server side optimization is enabled whenever server_learning_rate or server_momentum constructor parameters are set to values different from the defaults (here). As such, calling the FedAvgM constructor without any parameters works fine, while calling it with server_learning_rate = 0.9, for example, don't.

Considering all of that, it could be nice to add this information to the constructors' documentation, as to avoid confusion in the future.

[achiverram28]

I guess the assert is an explanatory point and agree with @DanielCardeal where the user can understand that if there is a server side optimisation , the initial_parameters should be done , but , for more clarity we can add it in the docstrings of the strategy class

[gubertoli]

Isn't FedAvgM about server side optimization with momentum?

[DanielCardeal]

Yes, @gubertoli.

It also seems a bit counterintuitive to allow users to initialize the strategy without initial_parameters since, in such cases, both FedAvg and FedAvgM aggregate the results in the exact same way.

I propose the changes in #2416 as a possible fix.