ref(worker): Amend function signature for coroutines

Coroutines have a return value, however the current function signature for the worker methods does not
accomodate for this. Therefore, this signature was changed.

GH-4578

Author: srothh

sentry_sdk/worker.py

@@ -34,7 +34,7 @@ def kill(self) -> None:
         pass
 
     def flush(
-        self, timeout: float, callback: Optional[Callable[[int, float], None]] = None
+        self, timeout: float, callback: Optional[Callable[[int, float], Any]] = None
     ) -> None:
         """
         Flush the worker.
@@ -50,7 +50,7 @@ def full(self) -> bool:
         pass
 
     @abstractmethod
-    def submit(self, callback: Callable[[], None]) -> bool:
+    def submit(self, callback: Callable[[], Any]) -> bool:
         """
         Schedule a callback to be executed by the worker.
 
@@ -149,7 +149,7 @@ def _wait_flush(self, timeout: float, callback: Optional[Any]) -> None:
                 pending = self._queue.qsize() + 1
                 logger.error("flush timed out, dropped %s events", pending)
 
-    def submit(self, callback: Callable[[], None]) -> bool:
+    def submit(self, callback: Callable[[], Any]) -> bool:
         self._ensure_thread()
         try:
             self._queue.put_nowait(callback)