input: Write a function to create a linked list in Python using the ListNode class. The function should take a list of integers and return the head of the linked list.
  
  class ListNode:
      def __init__(self, data):
          self.data = data
          self.next = None
  
  assert create_linked_list([1, 2, 3])==ListNode(1)
  assert create_linked_list([10, 20, 30])==ListNode(10)
  assert create_linked_list([5])==ListNode(5)
  assert create_linked_list([])==None
output: def create_linked_list(lst):
      if not lst:
          return None
      head = ListNode(lst[0])
      current = head
      for value in lst[1:]:
          current.next = ListNode(value)
          current = current.next
      return head