@Override
    public boolean isAcceptable(Object element, PsiElement context) {
      if (!(element instanceof RncDocument)) {
        return false;
      }

      final PsiFile file = ((RncDocument)element).getContainingFile();
      String namespace = null;
      if (file instanceof RncFile) {
        for (RncDecl decl : ((RncFile)file).getDeclarations()) {
          if (decl instanceof RncNsDecl) {
            namespace = decl.getDeclaredNamespace();
            break;
          }
        }
      }

      if (namespace != null) {
        for (String aMyValue : myValue) {
          if (aMyValue.equals(namespace)) return true;
        }
      }
      return false;
    }
@Override
    public boolean isAcceptable(Object element, PsiElement context)