code: def animate_flash(self, color, groups=('LEFT', 'RIGHT'), sleeptime=0.5, duration=5, block=True):
          
  
          def _animate_flash():
              even = True
              start_time = dt.datetime.now()
  
              while True:
                  if even:
                      for group in groups:
                          self.set_color(group, color)
                  else:
                      self.all_off()
  
                  if self.animate_thread_stop or duration_expired(start_time, duration):
                      break
  
                  even = not even
                  sleep(sleeptime)
  
              self.animate_thread_stop = False
              self.animate_thread_id = None
  
          self.animate_stop()
  
          if block:
              _animate_flash()
          else:
              self.animate_thread_id = _thread.start_new_thread(_animate_flash, ())
docs: Turn all LEDs in ``groups`` off/on to ``color`` every ``sleeptime`` seconds
  
          Animate for ``duration`` seconds.  If ``duration`` is None animate for forever.
  
          Example:
  
          .. code-block:: python
  
              from ev3dev2.led import Leds
              leds = Leds()
              leds.animate_flash('AMBER', sleeptime=0.75, duration=10)