ENH: support single-part multipolygons in Squareness and CentroidCorners

[songololo]

Is there appetite to support MultiPolygons for Squareness and CentroidCorners?

[martinfleis]

thanks for this!

I understand how useful it could be in some cases but am not sure if it doesn't bring a bit opaque inconsistency when it does work for some MultiPolygons but not for the other.

@jGaboardi what are your thoughts?

[jGaboardi]

I understand how useful it could be in some cases but am not sure if it doesn't bring a bit opaque inconsistency when it does work for some MultiPolygons but not for the other.

It seems to me that the opaque inconsistency can be cleared up with several more words in the docstring (and maybe a thrown warning silenced by default at the absolute most). My reasoning here is that the MultiPolygons that are being operated on are not true MultiPolygons, they are single Polygons mislabeled (perhaps not the best terminology) as being MultiPolygons. Maybe something like:

Returns ``np.nan`` for true MultiPolygons (containing multiple geometries).
MultiPolygons with a singular geometry are treated as Polygons.

And tests failing due to #508, not this PR, correct?

[martinfleis]

Okay, let's give it a shot following @jGaboardi's suggestion.

And tests failing due to #508, not this PR, correct?

Yes.

[martinfleis]

Thanks!