code: public static ContextAwarePolicy createPublicationsFilePolicy(PublicationsHandler handler, Extender extender) {
          Util.notNull(handler, "Publications handler");
          PolicyContext context = new PolicyContext(handler, extender != null ? extender.getExtendingService() : null);
          return new ContextAwarePolicyAdapter(new PublicationsFileBasedVerificationPolicy(), context);
      }
docs: Creates context aware policy using {@link PublicationsFileBasedVerificationPolicy} for verification. If
  extender is provided, then extending is allowed while verifying signature.
  
  @param handler
  Publications handler.
  @param extender
  Extender.
  @return Publications file based verification policy with suitable context.