from machine import Pin 
import time
led1 = Pin(4, Pin.OUT)
led2 = Pin(16, Pin.OUT) 
led3 = Pin(17, Pin.OUT) 

while True:
    led1.value(1) 
    led2.value(1) 
    led3.value(1) 
    time.sleep_ms(200) 
    led1.value(0)
    led2.value(0)
    led3.value(0)
    time.sleep_ms(200)