public function implicitWait($timeout)
    {
        $timeoutNormalize = intval(ceil($timeout / 100));
        if ($this->cache[self::WAIT_IMPLICIT] === $timeoutNormalize) {
            return null;
        }
        $this->cache[self::WAIT_IMPLICIT] = $timeout;
        $param = ['ms' => intval($timeout)];
        $command = $this->driver->factoryCommand('timeouts/implicit_wait', WebDriver_Command::METHOD_POST, $param);
        return $this->driver->curl($command)['value'];
    }