'Return target WWN'

def find_target_wwns(self):

    target_wwns = []
    target = ''
    url = ('/storage/arrays/%s/controllers' % self._get_ise_globalid())
    resp = self._send_cmd('GET', url)
    status = resp['status']
    if (status != 200):
        LOG.error('Controller    GET    failed    (%d)', status)
        RaiseXIODriverException()
    controllers = etree.fromstring(resp['content'])
    for controller in controllers.iter():
        if (controller.tag != 'controller'):
            continue
        fcports = controller.find('fcports')
        if (fcports is None):
            continue
        for fcport in fcports:
            if (fcport.tag != 'fcport'):
                continue
            wwn_tag = fcport.find('wwn')
            if (wwn_tag is None):
                continue
            target = wwn_tag.text
            target_wwns.append(target)
    return target_wwns
