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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 cart_db():
 """ return a pymongo db connection for interacting with cart objects """

    config = _config_file()
    _config_test(config)

    juicer.utils.Log.log_debug("Establishing cart connection:")
    cart_con = MongoClient(dict(config.items(config.sections()[0]))['cart_host'])
    cart_db = cart_con.carts

    return cart_db