Traceback (most recent call last):
  File "/app/code.py", line 32, in <module>
    print(ping(ball, bounce))
          ^^^^^^^^^^^^^^^^^^
  File "/app/code.py", line 27, in ping
    ball = pong(ball)
           ^^^^^^^^^^
  File "/app/code.py", line 16, in pong
    service = next(potential_services)
              ^^^^^^^^^^^^^^^^^^^^^^^^
StopIteration