src/vs/workbench/api/common/extHostEditorTabs.ts/ExtHostEditorTabGroup/activeTab
class ExtHostEditorTabGroup:	get apiObject(): vscode.TabGroup {
		if (!this._apiObject) {
			// Don't want to lose reference to parent `this` in the getters
			const that = this;
			const obj: vscode.TabGroup = {
				get isActive() {
					// We use a getter function here to always ensure at most 1 active group and prevent iteration for being required
					return that._dto.groupId === that._activeGroupIdGetter();
				},
				get viewColumn() {
					return typeConverters.ViewColumn.to(that._dto.viewColumn);
				},
				get activeTab() {
					return that._tabs.find(tab => tab.tabId === that._activeTabId)?.apiObject;
				},
				get tabs() {
					return Object.freeze(that._tabs.map(tab => tab.apiObject));
				}
			};
			this._apiObject = Object.freeze<vscode.TabGroup>(obj);
		}
		return this._apiObject;
	}