from machine import Pin
import time 
red=Pin(0.Pin.OUT)
green=Pin(1.Pin.OUT)
yellow=Pin(0.Pin.OUT)
while true:
red.value(0) 
green.value(1)
yellow.value(0)
time.sleep(1)
red.value(1)
green.value(0)
yellow.value(1)
time.sleep(1)