Any idea on how to implement a Many to Many relationship between two collections

[Lishenga]

Am trying to implement a Many to Many relationship between two collections in a MongoDB, i have done this

@ManyToMany({ entity: () => Product, owner: true })
selectedProducts = new Collection<Product>(this);

unfortunately the objectIds for the collection Product are not being persisted in the collection but other fields for the collection are being persisted. Any ideas on how to persist the objectids for the Many to Many relationship in MongoDB. Any assistance will be highly appreciated.