Fix slice indices failure.

[kattni]

Ran into an issue running the Chase animation in the LED Animation library: AttributeError: 'slice' object has no attribute 'indices'. Fixed it.

Tested on QT Py M0.

[kmatch98]

Looks good to me.

[dunkmann00]

I think this may introduce some potential bugs when the slice values are negative or if values greater than the sequence length are given. Here is the function that handles this in CircuitPython for reference of what needs to be handled: objslice function

But this actually raises the larger question of why did you get that error in the first place? slice objects should have an indices function.

[jepler]

Circuitpython's core code has support for "indices" but it's always been disabled (MICROPY_PY_BUILTINS_SLICE_INDICES). Interesting that the use of it slipped into pypixelbuf without notice. We could always try enablng it, it looks like it wouldn't add much code at all.

[dunkmann00]

@jepler I could be wrong but I think this was only introduced after the recent Micropython version merges. If you look at the CircuitPython 6.3 branch MICROPY_PY_BUILTINS_SLICE_INDICES is not present in objslice.c. And the other flags are turned on, so the indices function works.

I'm not able to verify that by testing at the moment, but I do remember when I worked on this library a while back indices was working.

[jepler]

OK, yeah, I see that. Mind filing an issue at circuitpython so someone can fix it? It does look like it regressed from 6.3 to main.

[dunkmann00]

Sure thing 👍