code: public void visitCollection(InvocationContext ctx, Collection<? extends VisitableCommand> toVisit) throws Throwable {
        for (VisitableCommand command : toVisit) {
           command.acceptVisitor(ctx, this);
        }
     }
docs: Helper method to visit a collection of VisitableCommands.
  
  @param ctx     Invocation context
  @param toVisit collection of commands to visit
  @throws Throwable in the event of problems