input: Write a function to delete a specified node from a linked list. If the head node holds the node to be deleted, update the head to the next node. If the node is not present in the linked list, do nothing.
  assert deleteNode(head, nodeToDelete) is None
  assert deleteNode(head, head) == newHead
  assert deleteNode(head, nonExistentNode) is None
  assert deleteNode(None, anyNode) is None
  assert deleteNode(singleNodeList, singleNodeList.head) is None
output: def deleteNode(head, nodeToDelete):
      if head is None:
          return None
      if head == nodeToDelete:
          return head.next
      current = head
      while current.next:
          if current.next == nodeToDelete:
              current.next = current.next.next
              return head
          current = current.next
      return head