from machine import Pin, Timer
from utime import sleep

led_bar_pins=[19,18,5,17,16,4,0,2,15,21]
led_bar= [Pin(led_bar_pins[i], Pin.OUT) for i in range(10)] 

def main():
    while True:
        sleep(10)

myTimer = Timer(1)

def toggle_led_bar(myTimer):
    for pin in led_bar:
        pin.on()
        sleep(0.5)
        pin.off()
        sleep(0.5)

myTimer.init(period=2000, mode=Timer.PERIODIC, callback=toggle_led_bar)

if __name__ == '__main__':
    main()