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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 get_availabilities_for_duration(duration, availabilities):
 """ Helper function to return the windows of availability of the given duration, when provided a set of 30 minute windows. """

    duration_availabilities = []
    start_time = '10:00'
    while start_time != '17:00':
        if start_time in availabilities:
            if duration == 30:
                duration_availabilities.append(start_time)
            elif increment_time_by_thirty_mins(start_time) in availabilities:
                duration_availabilities.append(start_time)

        start_time = increment_time_by_thirty_mins(start_time)

    return duration_availabilities