remove isinstance check

Author: miguelHx

Python/chapter02/2.4 - Partition/miguel_2.4_soln.py

@@ -92,9 +92,7 @@ def pop_head(self) -> Node:
         self.size -= 1
         return h
 
-    def append(self, ll: object):
-        if not isinstance(ll, LinkedList):
-            raise TypeError('not a linked list')
+    def append(self, ll: 'LinkedList') -> None:
         self.tail.next = ll.head
         self.size += ll.size