new_contents: class Solution:
      # @param {TreeNode} root the root of binary tree
      # @return {TreeNode} the max node
      def maxNode(self, root):
          if root == None:
              return None
              
          stack  = [root]
          curmax = root
          
          while len(stack) > 0:
              node   = stack.pop()
              curmax = max([node, curmax], key=lambda x: x.val)
              
              if node.left != None:
                  stack.append(node.left)
                  
              if node.right != None:
                  stack.append(node.right)
                  
          return curmax
  
subject: Rename binary_tree_maximum_node.py to binary_tree_maximum_node2.py