var persistence = BeaconsMongoDbPersistence();
//...

await persistence.open('test');

var beacon = BeaconV1(id: '1', site_id: '0001', udi: '0002');

await persistence.set('test', beacon);
var item = await persistence.getOneByUdi('test', '0002');
await persistence.close('test');
print(item!.udi); // Result: 0002