code: @Override
      public X509CRL fetch(final Resource crl) throws IOException, CRLException, CertificateException {
          val results = fetch(CollectionUtils.wrap(crl));
          if (!results.isEmpty()) {
              return results.iterator().next();
          }
          LOGGER.warn("Unable to fetch [{}]", crl);
          return null;
      }
docs: Fetch the resource. Designed so that extensions
  can decide how the resource should be retrieved.
  
  @param crl the resource
  @return the x 509 cRL
  @throws IOException          the exception thrown if resources cant be fetched
  @throws CRLException         the exception thrown if resources cant be fetched
  @throws CertificateException the exception thrown if resources cant be fetched