input: Write a function to create a linked list class in Python with a node class. The function should return the class definition as shown below.
  
  assert create_linked_list()==class ListNode:
      def __init__(self, data):
          self.data = data
          self.next = None
  
  assert create_linked_list().__name__=='ListNode'
output: def create_linked_list():
      class ListNode:
          def __init__(self, data):
              self.data = data
              self.next = None
      return ListNode