docs: public List<Extension> getExtensionsByUrl(String theUrl) {
        org.apache.commons.lang3.Validate.notBlank(theUrl, "theUrl must be provided with a value");
        ArrayList<Extension> retVal = new ArrayList<Extension>();
        for (Extension next : getExtension()) {
          if (theUrl.equals(next.getUrl())) {
            retVal.add(next);
          }
        }
        return Collections.unmodifiableList(retVal);
      }