def expand_leaf(node, state):
""" Adds a new leaf to the tree by creating a new child node for the given node.
Args:
node: The node for which a child will be added.
state: The state of the game.
Returns: The added child node.
######################
Expansion Phase
if unexplored child
expand (random order reduces bias)
if terminal state
return
"""
### testing syntax since using dict
if node.untried_actions: # if the node has any untried actions
# expand node
# __init__(self, parent=None, parent_action=None, action_list=[]):
move = choice(node.untried_actions)
state.apply_move(move)
new_node = MCTSNode(parent=node, parent_action=move, action_list=state.legal_moves)
node.untried_actions.remove(move)
new_node.parent = node
new_node.parent_action = move
new_node.action_list =state.legal_moves
node.child_nodes[move] = new_node
return new_node
return None
