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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 from_config(config_file, use_admin=False):
 """ Initialize a QueryEngine from a JSON config file generated using mgdb init. Args: config_file: Filename of config file. use_admin: If True, the admin user and password in the config file is used. Otherwise, the readonly_user and password is used. Defaults to False. Returns: QueryEngine """

        with open(config_file) as f:
            d = json.load(f)
            user = d["admin_user"] if use_admin else d["readonly_user"]
            password = d["admin_password"] if use_admin \
                else d["readonly_password"]
            return QueryEngine(
                host=d["host"], port=d["port"], database=d["database"],
                user=user, password=password, collection=d["collection"],
                aliases_config=d.get("aliases_config", None))