code: def GetAllUserSummaries():
    
    grr_api = maintenance_utils.InitGRRRootAPI()
    user_wrappers = sorted(grr_api.ListGrrUsers(), key=lambda x: x.username)
    summaries = [_Summarize(w.data) for w in user_wrappers]
    return "\n\n".join(summaries)
docs: Returns a string containing summary info for all GRR users.