from machine  import Pin
import utime

red = Pin(16, Pin.OUT)
green = Pin(18, Pin.OUT)
yellow = Pin(20, Pin.OUT)

red.value(0)
green.value(0)
yellow.value(0)

while True:
    red.value(1)
    utime.sleep(3)
    red.value(0)
    utime.sleep(.5)
    green.value(1)
    utime.sleep(5)
    green.value(0)
    utime.sleep(.5)
    yellow.value(1)
    utime.sleep(2)
    yellow.value(0)
    utime.sleep(.5)