Add missing section in classical shadows example

[Min-Li]

Description

Somehow a section has been deleted from the previous version, adding some docstrings

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License

• I license this contribution under the terms of the GNU GPL, version 3 and grant Unitary Fund the right to provide additional permissions as described in section 7 of the GNU GPL, version 3.

Before opening the PR, please ensure you have completed the following where appropriate.

• I added unit tests for new code.
• I used type hints in function signatures.
• I used Google-style docstrings for functions.
• I updated the documentation where relevant.
• Added myself / the copyright holder to the AUTHORS file

[codecov]

Codecov Report

Patch and project coverage have no change.

Comparison is base (be87d6f) 98.28% compared to head (cffc555) 98.28%.

Additional details and impacted files

@@           Coverage Diff           @@
##           master    #2026   +/-   ##
=======================================
  Coverage   98.28%   98.28%           
=======================================
  Files          86       86           
  Lines        4084     4084           
=======================================
  Hits         4014     4014           
  Misses         70       70           

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[andreamari]

Thanks @Min-Li for catching and fixing the problem!

[Min-Li]

Thanks for checking this out so fast @andreamari!