def groups(self, n):
        if len(self._items) > 1:
            root = _DendrogramNode(self._merge, *self._items)
        else:
            root = self._items[0]
        return root.groups(n)
Test the product filtering of the readout.
dataset/ETHPy150Open nltk/nltk/nltk/cluster/util.py/Dendrogram.groups--crossover with--dataset/ETHPy150Open mozilla/kitsune/kitsune/dashboards/tests/test_readouts.py/TemplateTranslationsTests.test_by_product