(re)initialize values to original state so the progressbar can be
        used (again)

def init(self):
        '''
        (re)initialize values to original state so the progressbar can be
        used (again)
        '''
        self.previous_value = None
        self.last_update_time = None
        self.start_time = None
        self.updates = 0
        self.end_time = None
        self.extra = dict()
        self._last_update_timer = timeit.default_timer()