Fix #3236

[h-mayorquin]

It would be nice if someone knew the exact expected behavior of this. The behavior is not documented in matplotilb.get_backend() as far as I can tell but this is how it works in my system:

https://matplotlib.org/stable/api/matplotlib_configuration_api.html#matplotlib.get_backend

Maybe something that changed recently:

[chrishalcrow]

Can confirm this fixes the bug on my Linux machine, and doesn't break anything on my Mac.

[zm711]

That would explain why I thought it worked fine. I had been doing it all on my mac for this stuff....

[JoeZiminski]

Can confirm this doesn't break anything on Windows either (could not reproduce #3236 on Windows), interestingly the output is completely different. I'm not sure why it's the same for both backends, I can confirm I have

ipympl 0.9.4
ipywidgets 8.1.3
matplotlib 

and restarting the kernel between the two:

[zm711]

This could be a very specific version issue, I don't which package. Not sure if we want to search for the root since it is so inconsistent or just use this PR to not worry about the assert.

[zm711]

Same as @JoeZiminski , I just tested this on Windows and couldn't replicate the issue. I get the same backend as Joe. But if I do %matplotlib ipympl it gives me a warning and says it will automatically switch to widget mode for me. But works fine.

[JoeZiminski]

Okay that's great @zm711 that it repliaces for you too, weird how different it is across platforms! I guess if its working cross-platform at the moment it makes sense to keep.

[h-mayorquin]

I will merge this as someone in #3236 is asking for this.