a helper method for creating a base 64 encoded secret key and digest
        :param secret_key: string with key to encrypt/decrypt data
        :return: string with base64 key, string with base64 digest

def _key_digest(self, secret_key):
        
        '''
            a helper method for creating a base 64 encoded secret key and digest
        :param secret_key: string with key to encrypt/decrypt data
        :return: string with base64 key, string with base64 digest
        '''
        
        from hashlib import md5, sha256
        from base64 import b64encode
        key_bytes = sha256(secret_key.encode('utf-8')).digest()
        key_b64 = b64encode(key_bytes).decode()
        digest_bytes = md5(key_bytes).digest()
        digest_b64 = b64encode(digest_bytes).decode()
        
        return key_b64, digest_b64