getCheckpoint method
Implementation
Future<Checkpoint> getCheckpoint(String id) async {
  final result = await client.request('sui_getCheckpoint', [id]);
  return Checkpoint.fromJson(result);
}Future<Checkpoint> getCheckpoint(String id) async {
  final result = await client.request('sui_getCheckpoint', [id]);
  return Checkpoint.fromJson(result);
}