from machine import Pin
from utime import sleep

red_led = Pin(2,Pin.OUT)
yellow_led = Pin(5,Pin.OUT)
green_led = Pin(10,Pin.OUT)

while True:
    #Red light
    red_led.on()
    yellow_led.off() 
    green_led.off()
    sleep(2) 

    #Yellow light
    red_led.off() 
    green_led.off()
    yellow_led.on()   
    sleep(2) 

    #Green light
    red_led.off()
    yellow_led.off() 
    green_led.on()
    sleep(1)