Fix mypy issues

Author: Cito

graphql/pyutils/event_emitter.py

@@ -1,4 +1,4 @@
-from typing import Callable, Dict, List
+from typing import cast, Callable, Dict, List, Optional
 
 from asyncio import AbstractEventLoop, Queue, ensure_future
 from inspect import isawaitable
@@ -11,7 +11,7 @@
 class EventEmitter:
     """A very simple EventEmitter."""
 
-    def __init__(self, loop: AbstractEventLoop=None) -> None:
+    def __init__(self, loop: Optional[AbstractEventLoop]=None) -> None:
         self.loop = loop
         self.listeners: Dict[str, List[Callable]] = defaultdict(list)
 
@@ -44,7 +44,8 @@ class EventEmitterAsyncIterator:
     """
 
     def __init__(self, event_emitter: EventEmitter, event_name: str) -> None:
-        self.queue: Queue = Queue(loop=event_emitter.loop)
+        self.queue: Queue = Queue(
+            loop=cast(AbstractEventLoop, event_emitter.loop))
         event_emitter.add_listener(event_name, self.queue.put)
         self.remove_listener = lambda: event_emitter.remove_listener(
             event_name, self.queue.put)

tests/subscription/test_map_async_iterator.py

@@ -5,6 +5,7 @@
 
 from graphql.subscription.map_async_iterator import MapAsyncIterator
 
+
 async def anext(iterable):
     """Return the next item from an async iterator."""
     return await iterable.__anext__()