public function getColumnMap()
    {
        $map = $this->getOption('column_map');

        if (null === $map) {
            $map = [];
            foreach ($this as $element) {
                $col = $element->getOption('span');
                if (null !== $col) {
                    $map[$element->getName()] = $col;
                }
            }

            $this->setOption('column_map', $map);
        }

        return $map;
    }