Creates and returns a new key-value pair to represent an entry in the content dictionary.
- macOS 10.5+
An object that represents the key-value pair. The object must not be autoreleased, and must implement the NSDictionaryControllerKeyValuePair informal protocol
This method is invoked for insertions of new key-value pairs, as well as transforming existing dictionary entries into key-value pairs for display. Objects returned by this method must implement the NSDictionaryControllerKeyValuePair informal protocol.
Subclass implementations must ensure that the object returned by
new is not autoreleased.