protected function addChannelFields(\DOMElement $channel)
{
foreach ($this->feed->getChannelFields() as $field) {
if ($field instanceof GroupChannelField) {
$parent = $this->dom->createElement($field->getName());
foreach ($field->getItemFields() as $childField) {
$child = $this->dom->createElement($childField->getName(), $childField->getValue());
$this->addAttributes($child, $childField);
$parent->appendChild($child);
}
} else {
$parent = $this->dom->createElement($field->getName(), $field->getValue());
}
$this->addAttributes($parent, $field);
$channel->appendChild($parent);
}
}