public IBaseMapper <T> Create(T obj)
{
AddToBsonClassMap(obj);
obj._id = ObjectId.GenerateNewId();
// sometimes adding to classmap does not add _t property to the document
// will also need to define our own type discriminator as we need to retrieve the value of it to do
// reflection, it requires namespace and class name, otherwise Type.GetType() may return null.
// this also allows us to do our own custom filtering by class type.
obj.ClassType = obj.GetType().FullName;
Uow.RegisterNew(CollectionName, obj.ToBsonDocument());
return(this);
}