from machine import Pin 
from time import sleep 

while True: 
    for i in range(2, 11, 2): 
        led = Pin(i, Pin.OUT) 
        led.value(1) 
        sleep(0.3) 
        led.value(0)
        
    for i in range(9, 0, -2): 
        led = Pin(i, Pin.OUT) 
        led.value(1) 
        sleep(0.3) 
        led.value(0)