from machine import Pin
import time

led_red=Pin(0,Pin.OUT)
led_green=Pin(7,Pin.OUT)
led_yellow=Pin(8,Pin.OUT)

while True:
    led_red.value(1)
    time.sleep(3)
    led_red.value(1)

    led_green.value(1)
    time.sleep(4)
    led_green.value(1)

    led_yellow.value(1)
    time.sleep(5)
    led_yellow.value(1)