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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 add_item(self, title, key, synonyms=None, description=None, img_url=None):
 """Adds item to a list or carousel card. A list must contain at least 2 items, each requiring a title and object key. Arguments: title {str} -- Name of the item object key {str} -- Key refering to the item. This string will be used to send a query to your app if selected Keyword Arguments: synonyms {list} -- Words and phrases the user may send to select the item (default: {None}) description {str} -- A description of the item (default: {None}) img_url {str} -- URL of the image to represent the item (default: {None}) """

        item = build_item(title, key, synonyms, description, img_url)
        self._items.append(item)
        return self