input: Write a function to delete a certain node from a linked list.
  assert deleteNode(Node(3, Node(5, Node(10))), Node(5)) == Node(3, Node(10))
  assert deleteNode(Node(3), Node(3)) == None
  assert deleteNode(Node(3, Node(5, Node(10))), Node(10)) == Node(3, Node(5))
  assert deleteNode(Node(3, Node(5)), Node(4)) == Node(3, Node(5))
  assert deleteNode(None, Node(3)) == None
output: def deleteNode(head, node):
      if head is None:
          return None
      if head.val == node.val:
          return head.next
      current = head
      while current.next:
          if current.next.val == node.val:
              current.next = current.next.next
              return head
          current = current.next
      return head