def merge(self, items):
        """
        Merge the collection with the given items.

        :param items: The items to merge
        :type items: list or Collection

        :rtype: Collection
        """
        if isinstance(items, BaseCollection):
            items = items.all()

        if not isinstance(items, list):
            raise ValueError('Unable to merge uncompatible types')

        self._items += items

        return self
Merge the collection with the given items.

        :param items: The items to merge
        :type items: list or Collection

        :rtype: Collection