Slight shape_index docstring modification to specify 2D array

[Yash-10]

Description

I was recently exploring the shape_index function and found some discussion here: https://mail.python.org/archives/list/scikit-image@python.org/thread/Q5FNUVXJBCB7YDAGHKTO7EUQORR7WMGF/ where, I think, @emmanuelle had suggested changing the docstring to explicitly state that 2D arrays are expected. From what I see, this change seems to not have been added yet, so I have tried to do it here.

Thanks!

Checklist

• Docstrings for all functions
• Gallery example in ./doc/examples (new features only)
• Benchmark in ./benchmarks, if your changes aren't covered by an
  existing benchmark
• Unit tests
• Clean style in the spirit of PEP8

For reviewers

• Check that the PR title is short, concise, and will make sense 1 year
  later.
• Check that new functions are imported in corresponding __init__.py.
• Check that new features, API changes, and deprecations are mentioned in
  doc/release/release_dev.rst.

[grlee77]

Thanks @Yash-10

I made a suggestion, but it would be good for other maintainers to confirm if this is indeed the style we settled on (I did not look up the issue just now)

[grlee77]

Suggested change

	image : 2D array
	image : (M, N) ndarray

I think this should probably be (M, N) ndarray, but haven't tracked down the issue where we discussed the style to use previously.

None of the functions in this corner.py file use that style, but many others in the library do (See for example haar.py, match.py, orb.py in this same folder)

[Yash-10]

Thanks for the suggestion!

[rfezzani]

I can not either remember if we already specified the style to use, but I think that you are right @grlee77: the style you are suggesting is already used in many places in the repo.

[mkcor]

Right. Apparently, we also have:

scikit-image/skimage/morphology/gray.py

Line 25 in 3ad3641

footprint : 2D array, shape (M, N)

in some places. Let's stick with (M, N) ndarray.

[rfezzani]

Thank you @Yash-10 for your contribution 😉