from time import sleep
from machine import Pin

led_red = Pin(2, Pin.OUT)
led_yellow = Pin(16, Pin.OUT)
led_green = Pin(17, Pin.OUT)

while True:
  led_red.value(1)
  sleep(3)
  led_red.value(0)
  led_yellow.value(1)
  sleep(1.5)
  led_yellow.value(0)
  led_green.value(1)
  sleep(3)
  led_green.value(0)