def __init__(self, key, b64secret, passphrase,
                 api_url="https://api.pro.coinbase.com"):
        """ Create an instance of the AuthenticatedClient class.

        Args:
            key (str): Your API key.
            b64secret (str): The secret key matching your API key.
            passphrase (str): Passphrase chosen when setting up key.
            api_url (Optional[str]): API URL. Defaults to cbpro API.
        """
        super(AuthenticatedClient, self).__init__(api_url)
        self.auth = CBProAuth(key, b64secret, passphrase)
        self.session = requests.Session()
 Create an instance of the AuthenticatedClient class.

        Args:
            key (str): Your API key.
            b64secret (str): The secret key matching your API key.
            passphrase (str): Passphrase chosen when setting up key.
            api_url (Optional[str]): API URL. Defaults to cbpro API.
        
cbpro/authenticated_client.py