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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_queue_class(config=None, queue_class=None):
 """ Return queue class from config or from RQ settings, otherwise return DjangoRQ. If ``queue_class`` is provided, it takes priority. The full priority list for queue class sources: 1. ``queue_class`` argument 2. ``QUEUE_CLASS`` in ``config`` argument 3. ``QUEUE_CLASS`` in base settings (``RQ``) """

    RQ = getattr(settings, 'RQ', {})
    if queue_class is None:
        queue_class = RQ.get('QUEUE_CLASS', DjangoRQ)
        if config:
            queue_class = config.get('QUEUE_CLASS', queue_class)

    if isinstance(queue_class, six.string_types):
        queue_class = import_attribute(queue_class)
    return queue_class