import RPi.Gimport time
GPIO.setmode(GPIO.BOARD)

GPIO.setup(15, GPIO.OUT)

p = GPIO.RWM(15,50)

p.start(7.5)

p.ChangeDutyCycle(7.5)
time.sleep(2)
p.Change.DutyCycle(12.5)
time.sleep(1)
p.Change.DutyCycle(2.5)
time.sleep(1)

p.stop()
GPIO.cleanup