add a cache toggle

[chrishavlin]

This is mostly for testing purposes, but maybe it'd be useful to include in the actual PR?

This PR adds a way to toggle the mask cache behavior for all the grids, the following would turn off/on cacheing:

ds = yt.load(...)
ds.index.set_grid_cache_mask(False) # Turn off
ds.index.set_grid_cache_mask(True) # Turn on

It includes an optional parameter, clear_all_data (default is True) to calls clear_all_data() if True.

[chrishavlin]

@matthewturk I can fix that type checking error if you think this would be a useful functionality to expose, but if we want to keep this branch just for testing then I won't bother fixing it :)

[matthewturk]

I do think it is worthwhile.

[chrishavlin]

removed the type hints i added to the new function cause it was triggering a type check for the whole class and I didn't want to get into fixing typing errors in this PR...

[chrishavlin]

I think I'll add a simple test too...

[chrishavlin]

glad i added a test -- clear_data() wasn't actually clearing the cached grid masks. So I adjusted the AMRGridPatch to reset the mask-related attributes.

[chrishavlin]

@matthewturk just FYI, I'm not planning on modifying this anymore unless you've got comments.

[matthewturk]

Looks great!

[matthewturk]

I'm slightly unsure about this being a top-level method, rather than having an underscore prefix. Then again, maybe it's good.

[chrishavlin]

Ya, I had the same thought. I think an underscore might be better? It's probably not something 99.9% of people would use. But maybe someone might find themselves in a memory-limited situation and want to disable cacheing easily?

So ya, I was on the fence, but happy to go with an underscore instead.

[matthewturk]

Let's do underscore, then I can merge and we'll PR upstream

[chrishavlin]

done