Collections\Dictionary::merge PHP Method

    public function merge($newItems)
    {
        if ($newItems instanceof self) {
            $newItems = $newItems->toArray();
        }
        if (!is_array($newItems)) {
            throw new \InvalidArgumentException('Combine must be a Dictionary or an array');
        }
        $items = array_merge($this->storage, $newItems);
        return new static($this->keyType, $this->valType, $items);
    }