[python] Fix retrieval of named levels from a MultiscaleImage

[aaronwolen]

Before this PR:

scene.img["tissue"].get_transform_to_level(0)
## <somacore.coordinates.ScaleTransform at 0x17701b390>

scene.img["tissue"].get_transform_to_level("hires")
## KeyError                                  Traceback (most recent call last)
## Cell In[325], line 1
## ----> 1 scene.img[image_name].get_transform_to_level("hires")
## 
## File ~/Library/CloudStorage/Dropbox-TileDB/Aaron Wolen/customers/czi/TileDB-SOMA2/apis/python/src/tiledbsoma/_multiscale_image.py:551, in MultiscaleImage.get_transform_to_level(self, level)
##     549             level_props = val
##     550         else:
## --> 551             raise KeyError("No level with name '{level}'")
##     552 else:
##     553     level_props = self._levels[level]
## 
## KeyError: "No level with name '{level}'"

With this PR:

scene.img["tissue"].get_transform_to_level(0)
## <somacore.coordinates.ScaleTransform object at 0x16f7667d0>

scene.img["tissue"].get_transform_to_level("hires")
## <somacore.coordinates.ScaleTransform object at 0x16f8189d0>

[codecov]

Codecov Report

Attention: Patch coverage is 0% with 6 lines in your changes missing coverage. Please review.

Project coverage is 86.49%. Comparing base (c2a34e5) to head (a42737f).
Report is 1 commits behind head on main.

Additional details and impacted files

@@             Coverage Diff             @@
##             main    #3119       +/-   ##
===========================================
+ Coverage   63.31%   86.49%   +23.18%     
===========================================
  Files         113       47       -66     
  Lines       14331     4924     -9407     
  Branches      855        0      -855     
===========================================
- Hits         9073     4259     -4814     
+ Misses       5050      665     -4385     
+ Partials      208        0      -208     

Flag	Coverage Δ
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python	86.49% <0.00%> (-0.08%)	⬇️

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Components	Coverage Δ
python_api	86.49% <0.00%> (-0.08%)	⬇️
libtiledbsoma	∅ <ø> (∅)