@classmethod<EOL><INDENT>def addCallback(cls, eventType, func, record=None, once=False):<DEDENT>
callbacks = cls.callbacks()<EOL>callbacks.setdefault(eventType, [])<EOL>callbacks[eventType].append((func, record, once))<EOL>
Adds a callback method to the class.  When an event of the given type is triggered, any registered
callback will be executed.

:param  eventType: <str>
:param  func: <callable>