def METHOD_NAME(self):
    records = [
        Record(0, 0),
        Record(1, 0),
        Record(2, 0),
        Record(3, 1),
        Record(4, 1),
        Record(5, 1),
        Record(6, 2),
    ]
    root = BuildTree(records)
    self.assert_node_is_branch(root, 0, 2)
    self.assert_node_is_branch(root.children[0], 1, 3)
    self.assert_node_is_branch(root.children[1], 2, 1)
    self.assert_node_is_leaf(root.children[0].children[0], 3)
    self.assert_node_is_leaf(root.children[0].children[1], 4)
    self.assert_node_is_leaf(root.children[0].children[2], 5)
    self.assert_node_is_leaf(root.children[1].children[0], 6)