def is_hidden_container(self, key, val):
        """
        The key is not one of the Mapfile keywords, and its
        values are a list
        """

        if key in ("layers", "classes", "styles", "symbols", "labels",
                   "outputformats", "features", "scaletokens",
                   "composites") and isinstance(val, list):
            return True
        else:
            return False