How to use the sshtunnel.SSHTunnelForwarder.get_keys function in sshtunnel

ssh_username=SSH_USERNAME,
            ssh_password=SSH_PASSWORD,
            remote_bind_address=(self.eaddr, self.eport),
            local_bind_address=('', self.randomize_eport()),
            logger=self.log
        ) as server:
            keys = server.get_keys()
            self.assertIsInstance(keys, list)
            self.assertFalse(any('keys loaded from agent' in l for l in
                             self.sshtunnel_log_messages['info']))

        tmp_dir = tempfile.mkdtemp()
        shutil.copy(get_test_data_path(PKEY_FILE),
                    os.path.join(tmp_dir, 'id_rsa'))

        keys = sshtunnel.SSHTunnelForwarder.get_keys(
            self.log,
            host_pkey_directories=[tmp_dir, ]
        )
        self.assertIsInstance(keys, list)
        self.assertTrue(
            any('1 keys loaded from host directory' in l
                for l in self.sshtunnel_log_messages['info'])
        )
        shutil.rmtree(tmp_dir)

def _consolidate_auth(ssh_password=None,
                          ssh_pkey=None,
                          ssh_pkey_password=None,
                          allow_agent=True,
                          host_pkey_directories=None,
                          logger=None):
        """
        Get sure authentication information is in place.
        ``ssh_pkey`` may be of classes:
            - ``str`` - in this case it represents a private key file; public
            key will be obtained from it
            - ``paramiko.Pkey`` - it will be transparently added to loaded keys

        """
        ssh_loaded_pkeys = SSHTunnelForwarder.get_keys(
            logger=logger,
            host_pkey_directories=host_pkey_directories,
            allow_agent=allow_agent
        )

        if isinstance(ssh_pkey, string_types):
            ssh_pkey_expanded = os.path.expanduser(ssh_pkey)
            if os.path.exists(ssh_pkey_expanded):
                ssh_pkey = SSHTunnelForwarder.read_private_key_file(
                    pkey_file=ssh_pkey_expanded,
                    pkey_password=ssh_pkey_password or ssh_password,
                    logger=logger
                )
            elif logger:
                logger.warning('Private key file not found: {0}'
                               .format(ssh_pkey))