src/app/dbtext/model/GroupedDbtextCollection.php
public function getKeys(): array {
		if (1 == count($this->dbtextCollections)) {
			return reset($this->dbtextCollections)->getKeys();
		}
		
		$keys = array();
		
		foreach ($this->dbtextCollections as $dbtextCollection) {
			array_push($keys, ...$dbtextCollection->getKeys());
		}
		
		return array_unique($keys);;
	}
public function getKeys(): array {
		if (1 == count($this->dbtextCollections)) {
			return reset($this->dbtextCollections)->getKeys();
		}
		
		$keys = array();
		
		foreach ($this->dbtextCollections as $dbtextCollection) {
			array_push($keys, ...$dbtextCollection->getKeys());
		}
		
		return array_unique($keys);;
	}
{@inheritDoc}
@see \dbtext\model\DbtextCollection::getKeys()