code: def add_user_to_group(self, group_name, user_name):
          
          params = {'GroupName' : group_name,
                    'UserName' : user_name}
          return self.get_response('AddUserToGroup', params)
docs: Add a user to a group
  
          :type group_name: string
          :param group_name: The name of the group
  
          :type user_name: string
          :param user_name: The to be added to the group.