Get all access keys associated with an account.

        :type user_name: string
        :param user_name: The username of the user

        :type marker: string
        :param marker: Use this only when paginating results and only in
                       follow-up request after you've received a response
                       where the results are truncated.  Set this to the
                       value of the Marker element in the response you
                       just received.

        :type max_items: int
        :param max_items: Use this only when paginating results to indicate
                          the maximum number of groups you want in the
                          response.

def get_all_access_keys(self, user_name, marker=None, max_items=None):
        """
        Get all access keys associated with an account.

        :type user_name: string
        :param user_name: The username of the user

        :type marker: string
        :param marker: Use this only when paginating results and only in
                       follow-up request after you've received a response
                       where the results are truncated.  Set this to the
                       value of the Marker element in the response you
                       just received.

        :type max_items: int
        :param max_items: Use this only when paginating results to indicate
                          the maximum number of groups you want in the
                          response.
        """
        params = {'UserName' : user_name}
        if marker:
            params['Marker'] = marker
        if max_items:
            params['MaxItems'] = max_items
        return self.get_response('ListAccessKeys', params,
                                 list_marker='AccessKeyMetadata')