public function keyBy($keyBy)
{
$keyBy = $this->valueRetriever($keyBy);
$results = [];
foreach ($this->items as $key => $item) {
$resolvedKey = $keyBy($item, $key);
if (is_object($resolvedKey)) {
$resolvedKey = (string) $resolvedKey;
}
$results[$resolvedKey] = $item;
}
return new static($results);
}