public ImageBuilder visible_when(IConstrainAnOperation func)
 {
     return(this);
 }
 public VisibilityConstrainedImage(IDrawAnImage original, IConstrainAnOperation constraint)
 {
     this.original   = original;
     this.constraint = constraint;
 }
 public ConstrainedMethod(IConstrainAnOperation constraint)
 {
     this.constraint = constraint;
 }