input: Write a python function to rotate binary tree nodes and ensure correct rotation directions.
  assert rotateNodes(TreeNode(1, TreeNode(2), TreeNode(3))).val == 2  # TreeNode(val, left, right) represents a binary tree node
  assert rotateNodes(TreeNode(4, None, TreeNode(5))).val == 5
  assert rotateNodes(TreeNode(6, TreeNode(7, None, TreeNode(8)), TreeNode(9))).val == 7
output: class TreeNode:
      def __init__(self, val=0, left=None, right=None):
          self.val = val
          self.left = left
          self.right = right
  
  def rotateNodes(root):
      if not root:
          return None
      if root.left:
          new_root = root.left
          root.left = new_root.right
          new_root.right = root
      elif root.right:
          new_root = root.right
          root.right = new_root.left
          new_root.left = root
      else:
          return root
      return new_root