Add docblock, fix formatting, fix implicit optional typing

sanic/signals.py

@@ -277,12 +277,18 @@ class SignalRouter(BaseRouter):
 
         return cast(Signal, signal)
 
-    def finalize(self, do_compile: bool = True, do_optimize: bool = False, loop: asyncio.AbstractEventLoop = None):
+    def finalize(
+        self,
+        do_compile: bool = True,
+        do_optimize: bool = False,
+        loop: Optional[asyncio.AbstractEventLoop] = None,
+    ):
         """Finalize the router and compile the routes
 
         Args:
             do_compile (bool, optional): Whether to compile the routes. Defaults to `True`.
             do_optimize (bool, optional): Whether to optimize the routes. Defaults to `False`.
+            loop (asyncio.AbstractEventLoop, optional): Event loop override for asyncio.get_running_loop().
 
         Returns:
             SignalRouter: The router