@NotNull
 /*package*/ static JetModifierListOwner addModifier(
     @NotNull PsiElement element,
     @NotNull JetKeywordToken modifier,
     @Nullable JetToken[] modifiersThatCanBeReplaced,
     @NotNull Project project,
     boolean toBeginning) {
   JetModifierListOwner newElement = (JetModifierListOwner) (element.copy());
   changeModifier(
       newElement,
       newElement.getModifierList(),
       newElement.getFirstChild(),
       modifiersThatCanBeReplaced,
       project,
       toBeginning,
       JetPsiFactory.createModifierList(project, modifier));
   return newElement;
 }