input: Write a function to implement a function in Python that takes a Huffman tree and drop all its leaf nodes. If the node is not None and doesn't have any children, it should be dropped. Don't change anything if the head is None. Recursively call the function on left and right subtrees and return the head of the modified tree. If the given tree is empty, return None.
  
  def dropLeafNodes(head): 
      
      # If node is not None and doesn't have any children 
      if head and not head.left and not head.right: 
          return None
    
      # Don't change anything if head is None 
      if not head: 
          return None
    
      # Recursively call dropLeafNodes on left and right subtrees
      head.left = dropLeafNodes(head.left) 
      head.right = dropLeafNodes(head.right) 
    
      # Return head of the modified tree
      return head
  
  assert dropLeafNodes(None) == None
  assert dropLeafNodes(((4,5),(6,7))) == ((None,None),(None,None))
  assert dropLeafNodes((1)) == None
  assert dropLeafNodes(((2,4),(5,6))) == ((None,None),(None,None))
  assert dropLeafNodes((3)) == None
output: def dropLeafNodes(head): 
      
      # If node is not None and doesn't have any children 
      if head and not head.left and not head.right: 
          return None
    
      # Don't change anything if head is None 
      if not head: 
          return None
    
      # Recursively call dropLeafNodes on left and right subtrees
      head.left = dropLeafNodes(head.left) 
      head.right = dropLeafNodes(head.right) 
    
      # Return head of the modified tree
      return head