from machine import Pin
from utime import sleep
led1 = Pin(2, Pin.OUT)
led2 = Pin(9, Pin.OUT)
led3 = Pin(28, Pin.OUT)
led4 = Pin(18, Pin.OUT)
while True:
    led1.on()
    led2.on()
    led3.on()
    led4.on()
    sleep(1)
    led1.off()
    led2.off()
    led3.off()
    led4.off()
    sleep(1)