input: 
  def isSubTree(T, S): 
      """ Check if the binary tree S is a subtree of binary tree T.
      
      >>> T1 = Node(1)
      >>> T1.left = Node(2)
      >>> T1.right = Node(3)
      >>> S1 = Node(2)
      >>> S1.left = Node(4)
      >>> S1.right = Node(5)
      >>> isSubTree(T1, S1)
      False
      >>> T2 = Node(5)
      >>> T2.left = Node(3)
      >>> T2.right = Node(7)
      >>> T2.left.left = Node(2)
      >>> T2.left.right = Node(4)
      >>> T2.right.right = Node(8)
      >>> S2 = Node(3)
      >>> S2.left = Node(2)
      >>> S2.right = Node(4)
      >>> isSubTree(T2, S2)
      True
      """
      if S is None: 
          return True
    
      if T is None: 
          return False
    
      if areIdentical(T, S): 
          return True
    
      return isSubTree(T.left, S) or isSubTree(T.right, S) 
    
    
  def areIdentical(T, S): 
        
      if T is None and S is None: 
          return True
    
      if T is None or S is None: 
          return False
    
      return (T.data == S.data and areIdentical(T.left, S.left)and
          areIdentical(T.right, S.right))
  
output:     if S is None: 
          return True
    
      if T is None: 
          return False
    
      if areIdentical(T, S): 
          return True
    
      return isSubTree(T.left, S) or isSubTree(T.right, S) 
    
    
  def areIdentical(T, S): 
        
      if T is None and S is None: 
          return True
    
      if T is None or S is None: 
          return False
    
      return (T.data == S.data and areIdentical(T.left, S.left)and
          areIdentical(T.right, S.right))