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pipeline = [
    {
        '$lookup': {
            'from': 'customers',
            'localField': 'customer_id',
            'foreignField': 'customer_id',
            'as': 'customer_info'
        }
    },
    {
        '$unwind': '$customer_info'
    },
    {
        '$group': {
            '_id': '$customer_info.location',
            'totalRevenue': {'$sum': '$price'}
        }
    }
]
result = list(orders.aggregate(pipeline))
for doc in result:
    print(doc)