Make Patch pickleable

[joouha]

Hello,

This makes Patch objects picklable by adding __getstate__ and __setstate__ methods.

This allows caching of callbacks which return Patch objects.

Currently pickling Patch objects results in a TypeError("'Patch' object is not callable") exception.

[T4rk1n]

💃 Looks good, thank you.

Can you add a changelog entry?

The failing tests in renderer seems unrelated

[joouha]

Done!

[alexcjohnson]

Oh interesting - is this for using Patch in a background callback? Or is there some other reason to pickle it?

[joouha]

@alexcjohnson My use case is simply so I can cache the result of a callback (as per the memoization example in the docs) - this was failing if the callback returned a Patch.

But I guess this would also allow background callbacks to return Patches too :-)