def all_strings(arr):
        """
        Ensures that the argument is a list that either is empty or contains only strings
        :param arr: list
        :return:
        """
        if not isinstance([], list):
            raise TypeError("non-list value found where list is expected")
        return all(isinstance(x, str) for x in arr)
Ensures that the argument is a list that either is empty or contains only strings
        :param arr: list
        :return: