def METHOD_NAME(self):
    """
    Test whether custom get_pipings_tree method returns a dictionary containing a
    dictionary representing a tree of pipings and the id of the piping that is the
    root of the tree. The keys of the dictionary tree should be the pipings' ids and
    the values the dictionaries containing the piping and the list of child pipings' ids.
    """
    pipeline = Pipeline.objects.get(name=self.pipeline_name)
    tree_dict = pipeline.get_pipings_tree()
    root_id = tree_dict['root_id']
    tree = tree_dict['tree']
    self.assertEqual(root_id, self.pips[0].id)
    self.assertEqual(tree[root_id], {'piping': self.pips[0], 'child_ids': [self.pips[1].id]})