code: public static IterationBuilderOver over()
      {
          Iteration iterationImpl = new Iteration(new TopLayerSingletonFramesSelector());
          iterationImpl.setPayloadManager(new NamedIterationPayloadManager(DEFAULT_SINGLE_VARIABLE_STRING));
          return iterationImpl;
      }
docs: Begin an {@link Iteration} over the selection that is placed on the top of the {@link Variables}. Also sets the name of the variable for this
  iteration's "current element" (i.e payload) to have the default value.