change Optional[Node] to Node return value

Author: miguelHx

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

@@ -83,7 +83,7 @@ def get_node_at(self, index: int) -> Node:
                 return n
             n = n.next
 
-    def pop_head(self) -> Optional[Node]:
+    def pop_head(self) -> Node:
         if self.head is None:
             raise IndexError('no head to pop')
         h = self.head