code: @Override
    boolean validateFree(SegmentKelp segment)
    {
      if (segment == _segment && isSwappable()) {
        PageLeafImpl leaf = null;
        
        if (_leafRef != null) {
          leaf = _leafRef.get();
        }
        
        System.out.println("\nSegment-free failed validation: " + this + " " + segment + " "+ leaf + "\n");
        
        return false;
      }
      
      return true;
    }
docs: On a segment free, validate that the page has no references.