text: class Node:
  
      def __init__(self, data) -> None:
          self.data = data 
          self.left = None
          self.right = None 
  
  def postOrder(root):
      if root is None:
              return
      result = []
  
      if  root.left is not None:
          result += postOrder(root.left)
  
      if root.right is not None:
          result += postOrder(root.right)
  
      while root.left == None and  root.right == None:
          return [root.data ]
      result.append(root.data)
          
      return result       
  
  
  
  if __name__ == "__main__":
      root = Node(10)
      root.left = Node(11)
      root.left.left = Node(7)
      root.right = Node(9)
      root.right.left = Node(15)
      root.right.right = Node(8)  
      print("Postorder traversal before insertion:", end = " ")
      print(postOrder(root))
      print()
  