from machine import Pin
from time import sleep
led1=Pin(1, Pin.OUT)
led2=Pin(2, Pin.OUT)
led3=Pin(3, Pin.OUT)
while True:
    led1.on()
    led2.on()
    led3.on()
    sleep(1)
    led1.off()
    led2.off()
    led3.off()
    sleep(1)