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----- ACCESS TO A SPECIFIC PRODUCT -----
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Main -> ProductRegister -> Product -> Warehouse -> Product

1: Through the main class we create a ProductRegister and fill it with Products.
2: Through the ProductRegister we gain access to a specific Product, for example Sausage A.
3: Through the product we gain access to which WareHouse it is located at.
4: Through the WareHouse we gain access to the specific Product that we want to look at.
5: Through the specific Product we gain access to the specific attributes of that Product, for example amount.