public function delFriendshipRequest($user_id, $user_decline_id)
    {
        if (!is_numeric($user_id) || 0 >= $user_id) {
            throw new InvalidArgumentException(
                "Api::addFriendshipRequest user_id field should be positive integer");
        }

        if (!is_numeric($user_decline_id) || 0 >= $user_decline_id) {
            throw new InvalidArgumentException(
                "Api::delFriendshipRequest user_decline_id field should be positive integer");
        }

        //@var $command Guzzle\Service\Command\AbstractCommand
        $command = $this->client->getCommand(
            'DeleteFriendshipRequest',
            array('id' => $user_id, 'user_decline_id' => $user_decline_id)
        );

        return $this->executeCommand($command);
    }