public function getHeader($name)
    {

        // map column => attribute name
        $name = $this->mapAttributeCodeByHeaderMapping($name);

        // query whether or not, the header is available
        if (isset($this->headers[$name])) {
            return $this->headers[$name];
        }

        // throw an exception, if not
        throw new \InvalidArgumentException(sprintf('Header %s is not available', $name));
    }