如何将节点字典转换为二叉树？[Python]

class TreeNode:
    def __init__(self, val=0, left=None, right=None):
        self.val = val
        self.left = left
        self.right = right

def dict_to_binary_tree(node_dict):
    if not node_dict:
        return None

    root = TreeNode(node_dict['val'])
    root.left = dict_to_binary_tree(node_dict.get('left'))
    root.right = dict_to_binary_tree(node_dict.get('right'))

    return root

node_dict = {
    'val': 1,
    'left': {
        'val': 2,
        'left': {
            'val': 4,
            'left': None,
            'right': None
        },
        'right': {
            'val': 5,
            'left': None,
            'right': None
        }
    },
    'right': {
        'val': 3,
        'left': None,
        'right': None
    }
}

root = dict_to_binary_tree(node_dict)

     1
   /   \
  2     3
 / \
4   5