code: function (url) {
          // url must be either string or an instance of url.
          if (!_.isString(url) && !Url.isUrl(url)) {
              return;
          }
  
          // find a certificate that can be applied to the url
          return this.find(function (certificate) {
              return certificate.canApplyTo(url);
          });
      }
docs: Matches the given url against the member certificates' allowed matches
  and returns the certificate that can be used for the url.
  
  @param {String} url The url to find the certificate for
  @return {Certificate~definition=} The matched certificate