public function getElements(string $key, $value): array
	{
		if (!isset($this->index[$key])) {
			throw new MissingAttrIndexException("Attribute index \"$key\" is not defined.");
		}

		return $this->index[$key][$value] ?? [];
	}
public function getElements(string $key, $value): array
	{
		if (!isset($this->index[$key])) {
			throw new MissingAttrIndexException("Attribute index \"$key\" is not defined.");
		}

		return $this->index[$key][$value] ?? [];
	}
public function getElements ( string $ key , $ value ) : array { if ( ! isset ( $ this -> index [ $ key ] ) ) { throw new MissingAttrIndexException ( "Attribute index \"$key\" is not defined." ) ; } return $ this -> index [ $ key ] [ $ value ] ?? [ ] ; }
Get elements by the value of the attribute
Get elements by the value of the attribute