If you want that link to WeightedAggregator to work, we'll need to expose it in the ```iris.analysis.__all__```. Not sure if that's in scope, so probably best leave it as-is, for now.

Also, we normally use a trick with the tidle, like this:
```
        Examples of aggregations that may be used include
        :data:`~iris.analysis.COUNT` and :data:`~iris.analysis.MAX`.

        Weighted aggregations :class:`~iris.analysis.WeightedAggregator` may
        also be supplied. These include :data:`~iris.analysis.MEAN` and
        :data:`~iris.analysis.SUM`.
```