def METHOD_NAME(self, timer):
    # set timer
    cur_time = time.time()
    deadline = cur_time + self.interval
    if self.blink_channels:
        self.fv.gui_do(self.fv.next_channel)
    else:
        self.fv.gui_do(self.fv.next_img, loop=True)
    timer.set(max(0.001, deadline - time.time()))