Description of the problem, including code/CLI snippet

Group Epics should have a milestone attribute

Expected Behavior

group_epic.milestone["iid"] should return a valid milestone iid if a milestone is set

Actual Behavior

AttributeError: 'GroupEpic' object has no attribute 'milestone'

Specifications

• python-gitlab version: 4.13.0
• Gitlab server version (or gitlab.com): 18.2