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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 iter_all_users(self, number=-1, etag=None, per_page=None):
 """Iterate over every user in the order they signed up for GitHub. :param int number: (optional), number of users to return. Default: -1, returns all of them :param str etag: (optional), ETag from a previous request to the same endpoint :param int per_page: (optional), number of users to list per request :returns: generator of :class:`User <github3.users.User>` """

        url = self._build_url('users')
        return self._iter(int(number), url, User,
                          params={'per_page': per_page}, etag=etag)