Please describe the question or issue you're facing with "Contribute to this documentation - Snapcraft documentation".

Follow https://documentation.ubuntu.com/snapcraft/latest/search/?q=build-packages&check_keywords=yes&area=default and observe lack of relevant documentation for a syntax element.

Moreover the syntax belongs under parts, yet is not found anywhere.

Reported from: https://documentation.ubuntu.com/snapcraft/latest/contribute-to-this-documentation/