from machine import Pin, Timer

pin_cords=[0,2,6]
ctr=0

pins=[Pin(pin_cords[i],Pin.OUT) for i in range (3)]


flag = 0
cnt = 0

timer = Timer()

def cycle_leds(timer):
    global flag
    global cnt
    for x in pins:
        x.off()
    
    pins[flag].on()
    cnt=cnt+1
    
    flag = (flag + 1) % 3  
    
    if cnt > 3:
        cnt = 0
        timer.init(period=1500, mode=Timer.PERIODIC, callback=cycle_leds)
    else:
        timer.init(period=150, mode=Timer.PERIODIC, callback=cycle_leds)

Timer(period=150, mode=Timer.PERIODIC, callback=cycle_leds)