text: # Definition for a binary tree node.
  # class TreeNode:
  #     def __init__(self, val=0, left=None, right=None):
  #         self.val = val
  #         self.left = left
  #         self.right = right
  class Solution:
      def invertTree(self, root: Optional[TreeNode]) -> Optional[TreeNode]:
          if root:
              root.left, root.right = root.right, root.left
              self.invertTree(root.left)
              self.invertTree(root.right)
          return root
  