public PredicateForm()
 {
     _form = new EmptyForm();
 }
 public PredicateForm(IPredicateForm form)
 {
     _form = form;
 }
 public PredicateForm(IPredicateForm form)
 {
     _form = form;
 }
 public PredicateForm()
 {
     _form = new EmptyForm();
 }