code: def portal(self, portalID=None):
          
          if portalID is None:
              portalID = self.portalSelf.id
          url = "%s/%s" % (self.root, portalID)
          return Portal(url=url,
                    securityHandler=self._securityHandler,
                    proxy_url=self._proxy_url,
                    proxy_port=self._proxy_port,
                    initalize=True)
docs: returns a specific reference to a portal