def _tree(self, i):
        node = self.get_by_address(i)
        word = node['word']
        deps = sorted(chain.from_iterable(node['deps'].values()))

        if deps:
            return Tree(word, [self._tree(dep) for dep in deps])
        else:
            return word
Test that this class inherits from the right classes.
dataset/ETHPy150Open nltk/nltk/nltk/parse/dependencygraph.py/DependencyGraph._tree--crossover with--dataset/ETHPy150Open brocaar/flask-views/flask_views/tests/unit/db/mongoengine/test_edit.py/BaseCreateViewTestCase.test_inherited_classes