from machine import Pin 
from time import sleep

red_led = Pin(0, Pin.OUT)
yellow_led = Pin(1, Pin.OUT)
green_led = Pin(2, Pin.OUT)

def flash_led (led, delay=1):
    led.on()
    sleep(delay)
    led.off()
    sleep(delay)

while True:
    flash_led(red_led, 2)
    flash_led (yellow_led, 0) 
    flash_led (green_led, 0.5)