Serve in order

arrivals is a list of customer names in the order they joined the line. Write serve_all(arrivals) that uses a deque to serve them one at a time from the front, and returns a list of the names in the order they were served. Do not change arrivals itself; the starter copies it into a deque for you.

serve_all(["Ada", "Grace", "Linus"])  ->  ["Ada", "Grace", "Linus"]

It looks trivial, and it is: the point is to write the queue loop once.

from collections import deque

def serve_all(arrivals):
    line = deque(arrivals)
    served = []
    while line:
        ...
    return served