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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_team_membership(self, auth, team_id, username):
 """ Add user to team. :param auth.Authentication auth: authentication object, must be admin-level :param str team_id: Team's id :param str username: Username of the user to be added to team :raises NetworkFailure: if there is an error communicating with the server :raises ApiFailure: if the request cannot be serviced """

        url = "/admin/teams/{t}/members/{u}".format(t=team_id, u=username)
        self.put(url, auth=auth)