TabSet constructor
Implementation
TabSet({this.defaultIndex = 0, required this.tabs})
: assert(!tabs.any((tab) => tab.tabIndex == null),
"No tabs index can be null"),
assert(tabs.length >= defaultIndex, "defaultIndex must be in tabSet"),
assert(tabs.map((t) => t.tabIndex).toSet().length == tabs.length,
"Must have unique tabs");