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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 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