How to Truncate Lineage Back to a Checkpoint in Python

class LineageNode:
    def __init__(self, name, parent=None, checkpoint=None):
        self.name = name
        self.parent = parent
        self.checkpoint = checkpoint

    def truncate_at_checkpoint(self):
        """Truncate lineage back to the last checkpoint."""
        current = self
        while current.checkpoint is None and current.parent is not None:
            current = current.parent
        return current if current.checkpoint is not None else None


def build_mock_lineage():
    """Create a mock pipeline with checkpoints at intermediate stages."""
    node_a = LineageNode("A")
    node_b = LineageNode("B", parent=node_a)
    node_c = LineageNode("C", parent=node_b)
    node_d = LineageNode("D", parent=node_c, checkpoint=True)
    node_e = LineageNode("E", parent=node_d)
    node_f = LineageNode("F", parent=node_e)
    return node_f


if __name__ == "__main__":
    leaf = build_mock_lineage()
    truncated = leaf.truncate_at_checkpoint()
    print(f"Leaf: {leaf.name}")
    print(f"Truncated at: {truncated.name if truncated else 'None'}")
    print(f"Full lineage: {leaf.name} -> {leaf.parent.name} -> {leaf.parent.parent.name} -> {leaf.parent.parent.parent.name}")