Update __process_response to Set next_url as None for Absent Values in atlas_probes.py

[mohamedawnallah]

Description

In atlas_probes.py, update __process_response to set next_url as None instead of an empty string (str()) to better indicate the absence of a next_url value in the crawler pipeline.

Motivation and Context

This change aligns with Python conventions by using None to signify the lack of a value. It improves readability and maintains compatibility since both None and an empty string evaluate to False.

How Has This Been Tested?

The script atlas_probes.py was run to ensure seamless functionality after the modification. Testing confirmed the script operates without issues with this update.

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)

Checklist:

• My code follows the code style of this project.
• My change requires a change to the documentation.
• I have updated the documentation accordingly.

[m-appel]

This is a bit of a philosophical discussion about what is better. Is there like a PEP or something that recommends the use of None? Personally, I like to keep return variables with the same type, although I can understand the argument that absence of a value should be None... I'm just saying this since this pattern will appear a lot on this codebase :)

If you want to assign None, we can also just delete the next_url = line entirely, since next_url = data['next'] will be None already.

[mohamedawnallah]

@m-appel, as far as I know, PEP 8 doesn't insist on using None for absent values. I might be biased as I used it frequently before. Let's stick with the convention established in the codebase 👍.