clear method
Remove all data in this instance and reset the auto increment values.
Implementation
Future<void> clear() async {
  for (final col in _collections.values) {
    await col.clear();
  }
}Remove all data in this instance and reset the auto increment values.
Future<void> clear() async {
  for (final col in _collections.values) {
    await col.clear();
  }
}