def __init__ (self, cv, id, ident = None, filterfunc = None, cachefs = None, callback = None):
        self._cv = cv
        self.id = id
        self.ident = ident
        self.filterfunc = filterfunc
        self.cachefs = cachefs
        self.callback = callback
        self.creation_time = time.time ()
        self.status = UNSENT
        self.result = None
        self.handler = None