input: def isSubTree(T: Node, S: Node) -> bool:
      """ Check if the binary tree S is a subtree of the binary tree T.
      >>> root_T = Node(26)
      >>> root_T.right = Node(3)
      >>> root_T.right.right = Node(3)
      >>> root_T.left = Node(10)
      >>> root_T.left.left = Node(4)
      >>> root_T.left.left.right = Node(30)
      >>> root_T.left.right = Node(6)
      >>> root_S = Node(10)
      >>> root_S.right = Node(6)
      >>> root_S.left = Node(4)
      >>> root_S.left.right = Node(30)
      >>> isSubTree(root_T, root_S)
      True
      >>> root_T = Node(1)
      >>> root_T.left = Node(2)
      >>> root_T.right = Node(3)
      >>> root_S = Node(4)
      >>> root_S.left = Node(5)
      >>> isSubTree(root_T, root_S)
      False
      """
output:     def areIdentical(root1, root2):
          if root1 is None and root2 is None:
              return True
          if root1 is None or root2 is None:
              return False
          return (root1.val == root2.val and
                  areIdentical(root1.left, root2.left) and
                  areIdentical(root1.right, root2.right))
  
      def isSubtreeUtil(T, S):
          if S is None:
              return True
          if T is None:
              return False
          if areIdentical(T, S):
              return True
          return isSubtreeUtil(T.left, S) or isSubtreeUtil(T.right, S)
  
      return isSubtreeUtil(T, S)