'List the groups that a specified user belongs to.
:type user_name: string
:param user_name: The name of the user to list groups for.
: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_groups_for_user(self, user_name, marker=None, max_items=None):

    params = {'UserName': user_name}
    if marker:
        params['Marker'] = marker
    if max_items:
        params['MaxItems'] = max_items
    return self.get_response('ListGroupsForUser', params, list_marker='Groups')
