src/vs/workbench/common/editor.ts/isEditorIdentifier
export function isEditorIdentifier(thing: unknown): thing is IEditorIdentifier {
	const identifier = thing as IEditorIdentifier | undefined;
	if (!identifier) {
		return false;
	}

	return typeof identifier.groupId === 'number' && !isUndefinedOrNull(identifier.editor);
}