'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.'

def add_user_to_group(self, group_name, user_name):

    params = {'GroupName': group_name, 'UserName': user_name}
    return self.get_response('AddUserToGroup', params)
