Role :data: is purposed for marking a module-level variable. [1] But role :attr: is often used instead in cases like sys.modules. While technically any module-level variable is accessible as an attribute, I think that it would be better to use more special role :data:.

[1] https://www.sphinx-doc.org/en/master/usage/restructuredtext/domains.html#role-py-data

Linked PRs

• gh-106892: Use roles :data: and :const: for referencing module variables #106894
• [3.12] gh-106892: Use roles :data: and :const: for referencing module variables (GH-106894) #106954
• [3.11] gh-106892: Use roles :data: and :const: for referencing module variables (GH-106894) #106955