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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def compute_busiest_date(feed: "Feed", dates: List[str]) -> str: """ Given a list of dates, return the first date that has the maximum number of active trips. Notes ----- Assume the following feed attributes are not ``None``: - Those used in :func:`compute_trip_activity` """

    f = feed.compute_trip_activity(dates)
    s = [(f[c].sum(), c) for c in f.columns if c != "trip_id"]
    return max(s)[1]