from machine import Pin
import utime

red = Pin(1, Pin.OUT)
yellow = Pin(5, Pin.OUT)
green = Pin(9, Pin.OUT)
while True :
    utime.sleep(0.5)
    red.toggle()
    utime.sleep(0.5)
    yellow.toggle()
    utime.sleep(0.5)
    green.toggle()
    utime.sleep(0.5)