anchor.diff:  
   
   BankAccount <-- IncomingInvoice
  +
  +Document <-- "0..1         " PaperclipForBankAccount
  +BankAccount <-- PaperclipForBankAccount
   
   
   class Document #lightgreen {
  
positive.code: class OrderItemInvoiceItemLink #pink {
  
  }
  
  IncomingInvoiceItem <--- OrderItemInvoiceItemLink
  OrderItem <--- OrderItemInvoiceItemLink
  
negative.code:     project: Project
  }
  
  class PaperclipForOrder #lightgreen {
  
  }
  
  Order <--> "0..*" OrderItem
  
  
  Party "buyer" <-- Order
  Party "seller" <-- Order
  
  
  Document <-- "0..1         " PaperclipForOrder
  Order <-- PaperclipForOrder
  
  
  
  