code: public function pluck($path, $defaultValue = null)
      {
          $result = [];
          if ($this->items === null || (is_array($this->items) && count($this->items) == 0)) {
              return null;
          }
          foreach ($this->items as $key => $item) {
              if (is_object($item)) {
                  $value = isset($item->{$path}) ? $item->{$path} : null;
              } else {
                  $value = Arr::get($item, $path, $defaultValue);
              }
              $result[] = $value;
          }
          return new static($result);
      }
docs: Pluck.
  
  @param string $path
  @param mixed $defaultValue Default null.
  @return $this