def update_tree(F, p, forest, k, left, obj_seq):
    """Update tree for tree-based non-dominated sorting."""
    _, M = F.shape
    if forest[k] is None:
        forest[k] = Tree(key=p, num_branch=M - 1)
        left[p] = False
    elif check_tree(F, p, forest[k], obj_seq, True):
        left[p] = False
Update tree for tree-based non-dominated sorting.
pymoo/functions/standard/non_dominated_sorting.py