mongodb-query.py

        pipeline = [
            {
                '$lookup': {
                    'from': 'students', 
                    'as': 'studentArray', 
                    'pipeline': [
                        {
                            '$sort': {
                                'balance_coins': -1
                            }
                        }, {
                            '$limit': 10
                        }
                    ]
                },
            }, 
            {
                '$project': {
                    'balance_coins': 1, 
                    'studentArray': {
                        '$filter': {
                            'input': '$studentArray', 
                            'as': 'student', 
                            'cond': {
                                '$eq': [
                                    '$$student.branch', 'IT'
                                ]
                            }
                }
                    }
                }
            }
        ]
        try:
            results = db.students_coins_balance.aggregate(pipeline)
        except Exception as e:
            print(e)