input: Write a function to create a class that represents a linked list node in Python. The class should have a constructor that initializes the node's data and sets the next node to None.
  class ListNode:
      def __init__(self, data):
          self.data = data
          self.next = None
  
  assert ListNode(5).data == 5
  assert ListNode(5).next == None
  assert ListNode("example").data == "example"
  assert ListNode("example").next == None
output: class ListNode:
      def __init__(self, data):
          self.data = data
          self.next = None