如果函数返回true，则返回包含该函数返回true的所有节点的树

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

def findNodes(root, func):
    if not root:
        return None
    
    result = []
    if func(root.val):
        result.append(root)
    
    left_subtree = findNodes(root.left, func)
    right_subtree = findNodes(root.right, func)
    
    if left_subtree:
        result.extend(left_subtree)
    if right_subtree:
        result.extend(right_subtree)
    
    if result:
        return TreeNode(root.val, left_subtree, right_subtree)
    else:
        return None