private static TensorType.Dimension tryParseMappedDimension(String element) {
        Matcher matcher = mappedPattern.matcher(element);
        if (matcher.matches()) {
            String dimensionName = matcher.group(1);
            return TensorType.Dimension.mapped(dimensionName);
        }
        return null;
    }
@param dimensionOrder if not null, this will be populated with the dimension names in the order they are written
vespajlib/src/main/java/com/yahoo/tensor/TensorTypeParser.java