Change _Shape to Shape and add comments for subclasses of Shape

[sooahleex]

Summary

• Related to Documentation API do not mention label property for dm.Bbox class #1555
• Change _Shape into Shape
  • If a class is marked as private: When a class name starts with an underscore (_), it is considered a private class and may be ignored by automatic documentation tools. To resolve this, try renaming the class to make it public.
• Add comments for subclasses of Shape

How to test

Checklist

• I have added unit tests to cover my changes.​
• I have added integration tests to cover my changes.​
• I have added the description of my changes into CHANGELOG.​
• I have updated the documentation accordingly

License

• I submit my code changes under the same MIT License that covers the project.
  Feel free to contact the maintainers if that's a concern.
• I have updated the license header for each file (see an example below).

# Copyright (C) 2024 Intel Corporation
#
# SPDX-License-Identifier: MIT

[codecov]

Codecov Report

Attention: Patch coverage is 94.44444% with 1 line in your changes missing coverage. Please review.

Project coverage is 81.03%. Comparing base (9bdf8de) to head (91752eb).
Report is 6 commits behind head on develop.

Files	Patch %	Lines
.../data_formats/datumaro_binary/mapper/annotation.py	66.66%	1 Missing ⚠️

Additional details and impacted files

@@           Coverage Diff            @@
##           develop    #1568   +/-   ##
========================================
  Coverage    81.03%   81.03%           
========================================
  Files          276      276           
  Lines        32430    32430           
  Branches      6595     6595           
========================================
  Hits         26280    26280           
  Misses        4696     4696           
  Partials      1454     1454           

Flag	Coverage Δ
ubuntu-20.04_Python-3.10	81.02% <94.44%> (ø)
windows-2022_Python-3.10	81.01% <94.44%> (ø)

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