from machine import Pin
from time import sleep

//# Define the pins
LED1 = Pin(1, Pin.OUT)
LED2 = Pin(5, Pin.OUT)
LED3 = Pin(9, Pin.OUT)

//# Infinite loop
while True:
//    # Turn the LEDs on
    LED1.on()
    LED2.on()
    LED3.on()

    //Wait for 0.5 seconds
    sleep(0.5)

    //# Turn the LEDs off
    LED1.off()
    LED2.off()
    LED3.off()

    //# Wait for 0.5 seconds
    sleep(0.5)