Beginner - Traffic Lights - Raspberry Pi

"""
filename:gpio_RPi_TrafficLights.py
Beginner Project - Traffic Lights
written by Trevor Olsson
© GPIO Support Services LTD MMXVII
More info here: http://www.gpio.co.uk/traffic-lights/
and here: https://gpiozero.readthedocs.io/en/stable/api_boards.html
"""

from gpiozero import TrafficLights
from time import sleep
traffic = TrafficLights(17,18,27,initial_value=False) # Choose outputs to use and turn off at start

while True:
    traffic.red.on()
    sleep(2)
    traffic.amber.on()
    sleep(2)
    traffic.red.off()
    traffic.amber.off()
    traffic.green.on()
    sleep(2)
    traffic.green.off()
    traffic.amber.on()
    sleep(2)
    traffic.amber.off()