input: Write a python function to insert a node at the beginning of a linked list using recursion.
  assert linked_list.head.data == 1
  linked_list.insert_at_head(Node(2))
  assert linked_list.head.data == 2
  linked_list.insert_at_head(Node(3))
  assert linked_list.head.data == 3
output: class Node:
      def __init__(self, data):
          self.data = data
          self.next = None
  
  class LinkedList:
      def __init__(self):
          self.head = None
  
      def insert_at_head(self, node):
          def recursive_insert(current_node):
              if current_node is None:
                  return node
              node.next = current_node
              return node
  
          self.head = recursive_insert(self.head)