public void Update(String ssn, Citizen citizenIn) => _citizen.ReplaceOne(citizen => citizen.SSN == ssn, citizenIn);
public void Remove(Citizen citizenIn) => _citizen.DeleteOne(citizen => citizen.SSN == citizenIn.SSN);
//CRUD operations
public Citizen Create(Citizen citizen)
{
_citizen.InsertOne(citizen);
return(citizen);
}