message: Update copy-list-with-random-pointer.py
diff: # Time: O(n)
  # Space: O(1)
  -class RandomListNode(object):
  +class Node(object):
  def __init__(self, x):
  - self.label = x
  + self.val = x
  self.next = None
  self.random = None
  @@ -14,7 +14,7 @@ class Solution(object):
  # copy and combine copied list with original list
  current = head
  while current:
  - copied = RandomListNode(current.label)
  + copied = Node(current.val)
  copied.next = current.next
  current.next = copied
  current = copied.next
  @@ -27,7 +27,7 @@ class Solution(object):
  current = current.next.next
  # split copied list from combined one
  - dummy = RandomListNode(0)
  + dummy = Node(0)
  copied_current, current = dummy, head
  while current:
  copied_current.next = current.next
  @@ -41,11 +41,11 @@ class Solution2(object):
  # @param head, a RandomListNode
  # @return a RandomListNode
  def copyRandomList(self, head):
  - dummy = RandomListNode(0)
  + dummy = Node(0)
  current, prev, copies = head, dummy, {}
  while current:
  - copied = RandomListNode(current.label)
  + copied = Node(current.val)
  copies[current] = copied
  prev.next = copied
  prev, current = prev.next, current.next
  @@ -69,12 +69,12 @@ class Solution3(object):
  :type head: RandomListNode
  :rtype: RandomListNode
  """
  - clone = defaultdict(lambda: RandomListNode(0))
  + clone = defaultdict(lambda: Node(0))
  clone[None] = None
  cur = head
  while cur:
  - clone[cur].label = cur.label
  + clone[cur].val = cur.val
  clone[cur].next = clone[cur.next]
  clone[cur].random = clone[cur.random]
  cur = cur.next
  