from gpiozero import AngularServo
from time import sleep

servo = AngularServo(17, min_angle=-90, max_angle=90)

while True:
    servo.angle = -90
    sleep(2)
    servo.angle = -45
    sleep(2)
    servo.angle = 0
    sleep(2)
    servo.angle = 45
    sleep(2)
    servo.angle = 90
    sleep(2)