input: Write a function to check if a given binary tree is a subtree of another binary tree. The function should return True if it is a subtree, otherwise return False. If any of the trees are empty, the function should return False.
  
  def isSubTree(T, S):
      
      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))
  
  assert isSubTree(Node(2), Node(2))==True
  assert isSubTree(Node(2), Node(3))==False
  assert isSubTree(None, Node(2))==False
  assert isSubTree(Node(2), None)==True
  assert isSubTree(Node(2, Node(3),Node(4)), Node(2, Node(3),Node(4)))==True
output: def isSubTree(T, S):
      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))