Linked list sorting (?)

leetcode/stdlib.py

@@ -0,0 +1,9 @@
+import typing
+
+
+class ListNode:
+    """ListNode is the leetcode "standard library" type used in linked lists"""
+
+    def __init__(self, val=0, next: typing.Optional["ListNode"] = None):  # no qa
+        self.val = val
+        self.next = next