code: protected void registerOptionHandlers() {
          try {
              for (Class c : Index.list(OptionHandlerExtension.class, Jenkins.getActiveInstance().pluginManager.uberClassLoader,Class.class)) {
                  Type t = Types.getBaseClass(c, OptionHandler.class);
                  CmdLineParser.registerHandler(Types.erasure(Types.getTypeArgument(t,0)), c);
              }
          } catch (IOException e) {
              throw new Error(e);
          }
      }
docs: Auto-discovers {@link OptionHandler}s and add them to the given command line parser.