def METHOD_NAME(self):
    """Returns the Flow Rate in l/min."""
    l_min = 0
    pulses = self.period_pulses()
    minutes = (time.time() - self._last_time) / 60
    if pulses:
        liters = pulses / self.pulses_per_l
        l_min = float(liters / minutes)
    self._last_time = time.time()
    return l_min, pulses