add items for tree
            :param data_dict: dict of tree data
            :param root: treeitemid of tree root
            :param target: treectrl obj

def add_items(self, data_dict, root=None, target=None):
        """ add items for tree
            :param data_dict: dict of tree data
            :param root: treeitemid of tree root
            :param target: treectrl obj
        """
        if root is None:
            print("Warning: TreeCtrl root must be given.")
            return
        if target is None:
            print("Warning: TreeCtrl target must be given.")
            return
        for k in sorted(data_dict):
            if isinstance(data_dict[k], dict):
                k_item_root = target.AppendItem(root, k)
                self.add_items(data_dict[k], k_item_root, target)
            else:
                item_val = ' : '.join((k, str(data_dict[k])))
                target.AppendItem(root, item_val)