fix: replace chained pandas indexing with .loc accessor

[SanjayUG]

Pull Request description

fix: replace chained pandas indexing with .loc accessor

• Resolves FutureWarning: ChainedAssignmentError warnings by using proper pandas DataFrame indexing methods.
• This change makes the code compatible with pandas 3.0's upcoming Copy-on-Write behavior.

Which issue this PR aims to resolve or fix?

Fixes #283

How to test these changes

• Run the code that previously triggered ChainedAssignmentError warnings.
• Verify that the warnings are no longer present.

Pull Request checklists

This PR is a:

• [x] bug-fix
• [ ] new feature
• [ ] maintenance

About this PR:

• [x] it includes tests.
• [ ] the tests are executed on CI.
• [ ] the tests generate log file(s) (path).
• [x] pre-commit hooks were executed locally.
• [ ] this PR requires a project documentation update.

Author's checklist:

• [x] I have reviewed the changes and it contains no misspelling.
• [x] The code is well commented, especially in the parts that contain more complexity.
• [x] New and old tests passed locally.

Additional information

Reviewer's checklist

Copy and paste this template for your review's note:

## Reviewer's Checklist

- [ ] I managed to reproduce the problem locally from the `main` branch
- [ ] I managed to test the new changes locally
- [ ] I confirm that the issues mentioned were fixed/resolved.