src/vs/workbench/browser/parts/editor/editorPart.ts/EditorPart/removeGroup
class EditorPart:	removeGroup(group: IEditorGroupView | GroupIdentifier): void {
		const groupView = this.assertGroupView(group);
		if (this.groupViews.size === 1) {
			return; // Cannot remove the last root group
		}

		// Remove empty group
		if (groupView.isEmpty) {
			return this.doRemoveEmptyGroup(groupView);
		}

		// Remove group with editors
		this.doRemoveGroupWithEditors(groupView);
	}