from machine import Pin 
import time
red=Pin(0,Pin.OUT)
green=Pin(1,Pin.OUT)
yello=Pin(2,Pin.OUT)
while True:
    red.value(1)
    green.value(0)
    yello.value(0)
    time.sleep(1)
    red.value(0)
    green.value(1)
    yello.value(0)
    time.sleep(1)
    red.value(0)
    green.value(0)
    yello.value(1)
    time.sleep(1)