chore: Restore the parts that were overwritten during conflict resolution.

[Nov1c444]

Summary

This line of code in graph.py was mistakenly deleted during conflict resolution when merging the plugin branch. It has now been re-merged.

Original PR: #13673

Checklist

[!IMPORTANT]
Please review the checklist below before submitting your pull request.

• [ ] This change requires a documentation update, included: Dify Document
• [x] I understand that this PR may be closed in case there was no previous discussion or issues. (This doesn't apply to typos!)
• [x] I've added a test for each change that was introduced, and I tried as much as possible to make a single atomic change.
• [x] I've updated the documentation accordingly.
• [x] I ran dev/reformat(backend) and cd web && npx lint-staged(frontend) to appease the lint gods