def update_with_move(self, last_move):
		if last_move in self.root.children:
			self.root = self.root.children[last_move]
			self.root.parent = None
			# siblings of root will be garbage-collected because they are no longer reachable
		else:
			self.root = TreeNode(None, 1.0)
step forward in the tree and discard everything that isn't still reachable
dataset/ETHPy150Open Rochester-NRT/RocAlphaGo/AlphaGo/mcts.py/MCTS.update_with_move