input: Write a class to create a linked list in Python nodes. The class should have a constructor that initializes the data and the next pointer. Additionally, provide an example of creating a ListNode object and ensuring the next pointer is set to None.
  
  class ListNode:
      def __init__(self, data):
          self.data = data
          self.next = None
  
  # Example
  node = ListNode(10)
  assert node.data == 10
  assert node.next == None
output: def __init__(self, data):
      self.data = data
      self.next = None