In a language that supports OOP paradigm, we have the following code that serializes the content of a shopping cart to JSON format:

class ShoppingCart
  private content : Dictionary<int, string> 

  public function serialize() : string
    return new JsonSerializer().serialize(content.clone())
  end function
end class

class JsonSerializer  
  public function serialize(value : Dictionary<int, string>) : string
    ' Code that serializes dictionary to JSON format and returns it as string
  end function
end class

A client wants to have the possibility of allowing loosely coupled plugins to be able to serialize the shopping cart content to their own formats (e.g., XML). Select lines of code that, together, would extend the code above to allow this.