public function removeAt($index)
{
$this->validateIndex($index);
$items = $this->items;
$partA = array_slice($items, 0, $index);
$partB = array_slice($items, $index + 1, count($items));
$items = array_merge($partA, $partB);
$col = new static($this->type);
$col->setItemsFromTrustedSource($items);
return $col;
}