Resolve code smells from Sonar Cloud in Python side

[TonyXiang8787]

As suggested in Sonar Cloud

https://sonarcloud.io/summary/new_code?id=PowerGridModel_power-grid-model

• Solve the code smell
• Ignore it in the sonar-project.properties if that's the intended choice. Document in this file about the design choice.

[mgovers]

there are only 2 code smells left after #491 . i think it's a good idea to try to pick this up in the near future.

@ekiwaka if you would like to do this as part 2 of your change, that would be great

[ekiwaka]

@mgovers Sure, I will pick it up.

[mgovers]

@ekiwaka how is it going? do you need any help? Or can I unassign you?