from machine import Pin
from time import sleep
while True:
    for i in range (2,11,2):
        led = Pin(i,Pin.Out)
        led.on()
        sleep(.3)
        led.off()
    for i in range (9,0,-2):
        led = Pin(i,Pin.Out)
        led.on()
        sleep(.3)
        led.off()