Minor cosmetic changes

Author: noxdafox

pebble/pool/base_pool.py

@@ -76,7 +76,7 @@ def join(self, timeout: float = None):
             self.stop()
             self.join()
         else:
-            self._context.task_queue.put(None)
+            self._context.task_queue.put(None)  # Pool termination sentinel
             self._stop_pool()
 
     def _wait_queue_depletion(self, timeout: Optional[float]):

pebble/pool/channel.py

@@ -141,7 +141,7 @@ def __init__(self, mp_context: multiprocessing.context.BaseContext):
     def __getstate__(self):
         return self.reader_mutex, self.writer_mutex
 
-    def __setstate__(self, state):
+    def __setstate__(self, state: tuple):
         self.reader_mutex, self.writer_mutex = state
         self.acquire = self._make_acquire_method()
         self.release = self._make_release_method()

pebble/pool/process.py

@@ -169,7 +169,7 @@ def task_scheduler_loop(pool_manager: 'PoolManager'):
                 else:
                     pool_manager.schedule(task)
             else:
-                task_queue.task_done()
+                task_queue.task_done()  # Termination sentinel received
     except BrokenProcessPool:
         context.status = PoolStatus.ERROR
 
@@ -324,7 +324,7 @@ def timeout_tasks(self) -> tuple:
 
     def cancelled_tasks(self) -> tuple:
         return tuple(t for t in dictionary_values(self.tasks)
-                     if t.timestamp != 0 and t.future.cancelled())
+                     if t.started and t.future.cancelled())
 
     @staticmethod
     def timeout(task: Task) -> bool: