How to use the ocflib.lab.stats.UtilizationProfile.from_hostnames function in ocflib

def get_daily_plot(day: date) -> Figure:
    """Return matplotlib plot representing a day's plot."""
    start, end = get_open_close(day)
    desktops = list_desktops(public_only=True)
    profiles = UtilizationProfile.from_hostnames(desktops, start, end).values()
    desks_count = len(desktops)

    now: Any = datetime.now()
    latest = min(end, now)
    minute = timedelta(minutes=1)
    times = [start + i * minute for i in range((latest - start) // minute + 1)]
    if now >= end or now <= start:
        now = None
    sums = []

    for t in times:
        instant15 = t + timedelta(seconds=15)
        instant45 = t + timedelta(seconds=45)
        in_use = sum(1 if profile.in_use(instant15) or profile.in_use(instant45) else 0 for profile in profiles)
        sums.append(in_use)

if __name__ == '__main__':
    start = datetime(2015, 11, 23)
    end = start + timedelta(days=1)

    print('Testing naive time to create profiles.')
    with timeit():
        slow_profiles = {
            host + '.ocf.berkeley.edu': UtilizationProfile.from_hostname(host, start, end)
            for host in list_desktops()
        }

    print('Testing optimized time to create profiles.')
    with timeit():
        fast_profiles = UtilizationProfile.from_hostnames(list_desktops(), start, end)

open_, close = get_open_close(date.today())
    now = datetime.today()

    # If the lab has opened, but hasn't closed yet, only count
    # statistics until the current time. If the lab isn't open
    # yet, then don't count anything, and if it is closed, show
    # statistics from when it was open during the day.
    if now > open_ and now < close:
        end = now
    elif now <= open_:
        end = open_
    else:
        end = close

    return sorted(
        UtilizationProfile.from_hostnames(list_desktops(), open_, end).values(),
        key=attrgetter('hostname'),
    )