cancel

A method that will be called when a load is no longer relevant and has been cancelled. This method does not need to guarantee that any in process loads do not finish. It also may be called before a load starts or after it finishes.

The best way to use this method is to cancel any loads that have not yet started, but allow those that are in process to finish since its we typically will want to display the same resource in a different view in the near future.

Note - this method will be run on the main thread so it should not perform blocking operations and should finish quickly.