/**
* @param null|int $index
*/
public function start($index = null)
{
if ($this->sheetWrapper->getObject() === null) {
throw new \LogicException();
}
if ($index !== null && !is_int($index)) {
throw new \InvalidArgumentException();
}
if ($index === null) {
$this->sheetWrapper->increaseRow();
} else {
$this->sheetWrapper->setRow($index);
}
}
