input: Write a function to delete a certain node from a linked list. The function should accept the node to be deleted as an argument and should not return anything. If the node is not found in the list, the function should do nothing. The linked list is implemented using a Node class and a LinkedList class.
  
  assert deleteNode(node_instance)==None
  assert deleteNode(None)==None
output: def deleteNode(node):
      if node is None or node.next is None:
          return
      node.val = node.next.val
      node.next = node.next.next