/**
* @inheritdoc
*/
public function start()
{
if (!$this->file) {
throw new \LogicException('Set a file first');
}
if ($this->writer) {
throw new \LogicException('Writer already started');
}
$this->writer = new BaseXmlWriter();
$this->writer->openUri($this->file->getPathname());
$this->writer->setIndent($this->indent);
$this->writer->startDocument('1.0', 'UTF-8');
$this->write(sprintf('<%s>', $this->rootNode));
}