code: public function tc($ns, N2nLocale ...$n2nLocales): DbtextCollection {
  		if (empty($n2nLocales)) {
  			$n2nLocales[] = $this->n2nContext->getN2nLocale();
  		}
  		
  		if (!is_array($ns)) {
  			return $this->getOrCreateBasicDbCollection($ns, ...$n2nLocales);
  		} elseif (count($ns) === 1) {
  			return $this->getOrCreateBasicDbCollection(reset($ns), ...$n2nLocales);
  		}
  		
  		$dbtextCollections = array();
  		foreach ($ns as $namespace) {
  			$dbtextCollections[] = $this->getOrCreateBasicDbCollection($namespace, ...$n2nLocales);
  		}
  
  		return new GroupedDbtextCollection($dbtextCollections, $n2nLocales);
  	}
docs: Returns fitting {@see TextCollection}
  
  @param string|string[] $ns
  @return DbtextCollection