code: public void beginStep(StepProgress prog, int step, String title) {
      if(prog != null) {
        prog.beginStep(step, title, this);
      }
    }
docs: Begin a new algorithm step (unless {@code null}).
  
  <b>Important:</b> Do not use this method when the parameter are not static.
  In these cases, check whether logging is enabled first, to avoid computing
  method parameters!
  
  @param prog Progress to increment, may be {@code null}.
  @param step Step number
  @param title Step title