'string or None if unknown'

@property
def description(self):

    name = None
    try:
        name = self._TYPE_NAMES[self.audioObjectType]
    except IndexError:
        pass
    if (name is None):
        return
    if (self.sbrPresentFlag == 1):
        name += '+SBR'
    if (self.psPresentFlag == 1):
        name += '+PS'
    return text_type(name)
