def METHOD_NAME(self, service_url):
    """Return a capabilities url
    @type service_url: string
    @param service_url: base url of WCS service
    @rtype: string
    @return: getCapabilities URL
    """
    qs = []
    if service_url.find('?') != -1:
        qs = parse_qsl(service_url.split('?')[1])
    params = [x[0] for x in qs]
    if 'service' not in params:
        qs.append(('service', 'WCS'))
    if 'request' not in params:
        qs.append(('request', 'GetCapabilities'))
    if ('version' not in params) and (self.version is not None):
        qs.append(('version', self.version))
    urlqs = urlencode(tuple(qs))
    return service_url.split('?')[0] + '?' + urlqs