🚀 Pull Request Checklist

✅ Summary

This PR solves the bug described in #393

🔄 Changes

• Added function _PK2d_term to legendre multipoles class, which is in charge of retrieving the 2d spectrum from the specified non-linear code and add the effect from observational systematics
• Substituted call to 2d method of the non-linear code with the function from the previous item

📝 Documentation

• This PR updates documentation
• This PR does not require documentation changes
• Issue created for documentation update: Don't forget to link the task!

🏗 Related Issues

Resolves #393

📸 Screenshots (if applicable)

Now cases 2 and 3 shown in the task description of #393 are fixed:

✅ PR Checklist for Developers

• I have titled this PR before merging as "gh-#:", where "#" represents the task it closes
• I have run locally pre-commit using pre-commit run --all-files
• I have tested my changes locally
• No new warnings or errors introduced
• I have updated documentation (if applicable)
• My changes do not introduce breaking changes (i.e: the package still gets installed)
• I have added unit tests (if applicable)
• I have consistently updated the GitHub information for the project, including milestones, task types, and other relevant details.

✅ PR Checklist for Reviewers

• The next PR targets the correct branch
• CI tests have run and passed for the latest commit on the source branch
• Check that the code can still be installed if new packages are imported
• If necessary, the notebooks in the playground will be updated in a corresponding follow-up PR
• Coverage percentage is retained or increased
• Quality of new/changed code is acceptable
• Quality of new/changed unit tests is acceptable
• No data files have been included in the commits
• Implementation follows the agreed task description point by point
• Check that any added folder/file has been added to the README.md file
• Check that the documentation has been updated accordantly
• Check that the corresponding branch has been deleted after merging. If not, delete it