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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, link, description, author_email=None, author_name=None, author_link=None, pubdate=None, comments=None, unique_id=None, enclosure=None, categories=(), item_copyright=None, ttl=None, **kwargs):
 """ Adds an item to the feed. All args are expected to be Python Unicode objects except pubdate, which is a datetime.datetime object, and enclosure, which is an instance of the Enclosure class. """

        to_unicode = lambda s: force_text(s, strings_only=True)
        if categories:
            categories = [to_unicode(c) for c in categories]
        if ttl is not None:
            # Force ints to unicode
            ttl = force_text(ttl)
        item = {
            'title': to_unicode(title),
            'link': iri_to_uri(link),
            'description': to_unicode(description),
            'author_email': to_unicode(author_email),
            'author_name': to_unicode(author_name),
            'author_link': iri_to_uri(author_link),
            'pubdate': pubdate,
            'comments': comments,
            'unique_id': to_unicode(unique_id),
            'enclosure': enclosure,
            'categories': categories or (),
            'item_copyright': to_unicode(item_copyright),
            'ttl': ttl,
        }
        item.update(kwargs)
        self.items.append(item)