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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 list_former(self):
 """List all former groups. :return: a list of groups :rtype: :class:`list` """

        url = utils.urljoin(self.url, 'former')
        response = self.session.get(url)
        return [Group(self, **group) for group in response.data]