The animation group to which the entry belongs.
- watchOS 2.0+
Use animation groups to created animated transitions between some, but not all, timeline entries. During Time Travel, ClockKit creates transition animations between entries with different group identifiers. ClockKit also creates transitions between entries whose identifiers are both
nil. When the group identifiers are the same, ClockKit does not create transition animations.
The group identifier is used only to determine whether transition animations should be created. The contents of the string may be anything that helps you identify the group to your app.