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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 all(cls):
 """ List all queues in MongoDB via aggregation, with their queued jobs counts. Might be slow. """


        # Start with raw queues we know exist from the config
        queues = {x: 0 for x in Queue.get_queues_config()}

        stats = list(context.connections.mongodb_jobs.mrq_jobs.aggregate([
            {"$match": {"status": "queued"}},
            {"$group": {"_id": "$queue", "jobs": {"$sum": 1}}}
        ]))

        queues.update({x["_id"]: x["jobs"] for x in stats})

        return queues