Installs an AppleEvent handler. classe and type are the
four-character OSA Class and Type designators, '****' wildcards
are allowed. When a matching AppleEvent is received the parameters are
decoded and your callback is invoked.
Your callback is called with the OSA Direct Object as first positional
parameter. The other parameters are passed as keyword arguments, with
the 4-character designator as name. Three extra keyword parameters are
passed: _class and _type are the Class and Type
designators and _attributes is a dictionary with the AppleEvent
The return value of your method is packed with
aetools.packevent() and sent as reply.
Note that there are some serious problems with the current
design. AppleEvents which have non-identifier 4-character designators
for arguments are not implementable, and it is not possible to return
an error to the originator. This will be addressed in a future