The differences between callback types?

I have to rework my callback plugin. I noticed there’s a variable called “CALLBACK_TYPE” and depending on which one you use, you can grab certain values. Where the heck can I find more documentation regarding this?

CALLBACK_TYPE is really not important currently unless the CALLBACK_TYPE is defined as stdout.

CALLBACK_TYPE is only used in ansible.executor.task_queue_manager.TaskQueueManager.load_callbacks to only load a single stdout callback. All others should work identically.

The really isn’t any documentation of these options, pretty much just the code in that function I specify above.