'register viewer: Registers an application as a ÔspecialÕ viewer for this MIME type. The application will be launched with ViewDoc events
Required argument: Application sig
Keyword argument MIME_type: MIME type viewer is registering for
Keyword argument with_file_type: Mac file type for the downloaded files
Keyword argument _attributes: AppleEvent attribute dictionary
Returns: TRUE if registration has been successful'

def register_viewer(self, _object, _attributes={}, **_arguments):

    _code = 'WWW!'
    _subcode = 'RGVW'
    aetools.keysubst(_arguments, self._argmap_register_viewer)
    _arguments['----'] = _object
    (_reply, _arguments, _attributes) = self.send(_code, _subcode, _arguments, _attributes)
    if _arguments.get('errn', 0):
        raise aetools.Error, aetools.decodeerror(_arguments)
    if _arguments.has_key('----'):
        return _arguments['----']
