Ensure an item is inserted to a list or create a new empty list

        :param new_items: the item(s) to insert
        :type new_items: list(obj)
        :param insert_to: the list on which to insert the items at index 0
        :type insert_to: list()

def _ensure_insert(self, new_items, insert_to):
        """Ensure an item is inserted to a list or create a new empty list

        :param new_items: the item(s) to insert
        :type new_items: list(obj)
        :param insert_to: the list on which to insert the items at index 0
        :type insert_to: list()
        """
        insert_to = insert_to or []
        insert_to.insert(0, new_items)
        return insert_to