public List<String> getTagsAt(int offset) {
        try {
            return ports.get(offset);
        } catch (IndexOutOfBoundsException e) {
            throw new IllegalArgumentException("Trying to get ports meta with offset " + offset +
                                               ", which is outside the range 0 to " + ports.size(), e);
        }
    }
Get an iterator of the Strings registered at the specific point.

@param offset the relative offset to inquire about tags
@return List of tags.
config-model/src/main/java/com/yahoo/vespa/model/PortsMeta.java