Modernize streaming example script

- add typing,
- apply multi-line call style,
- use 'cancel' log level,
- enable debug mode.

examples/full_fledged_streaming_service.py

@@ -1,6 +1,11 @@
 import time
 import trio
 import tractor
+from tractor import (
+    ActorNursery,
+    MsgStream,
+    Portal,
+)
 
 
 # this is the first 2 actors, streamer_1 and streamer_2
@@ -12,14 +17,18 @@ async def stream_data(seed):
 
 # this is the third actor; the aggregator
 async def aggregate(seed):
-    """Ensure that the two streams we receive match but only stream
+    '''
+    Ensure that the two streams we receive match but only stream
     a single set of values to the parent.
-    """
-    async with tractor.open_nursery() as nursery:
-        portals = []
+
+    '''
+    an: ActorNursery
+    async with tractor.open_nursery() as an:
+        portals: list[Portal] = []
         for i in range(1, 3):
-            # fork point
-            portal = await nursery.start_actor(
+
+            # fork/spawn call
+            portal = await an.start_actor(
                 name=f'streamer_{i}',
                 enable_modules=[__name__],
             )
@@ -43,7 +52,11 @@ async def aggregate(seed):
         async with trio.open_nursery() as n:
 
             for portal in portals:
-                n.start_soon(push_to_chan, portal, send_chan.clone())
+                n.start_soon(
+                    push_to_chan,
+                    portal,
+                    send_chan.clone(),
+                )
 
             # close this local task's reference to send side
             await send_chan.aclose()
@@ -60,7 +73,7 @@ async def aggregate(seed):
 
             print("FINISHED ITERATING in aggregator")
 
-        await nursery.cancel()
+        await an.cancel()
         print("WAITING on `ActorNursery` to finish")
     print("AGGREGATOR COMPLETE!")
 
@@ -75,18 +88,21 @@ async def main() -> list[int]:
 
     '''
     # yes, a nursery which spawns `trio`-"actors" B)
-    nursery: tractor.ActorNursery
-    async with tractor.open_nursery() as nursery:
+    an: ActorNursery
+    async with tractor.open_nursery(
+        loglevel='cancel',
+        debug_mode=True,
+    ) as an:
 
         seed = int(1e3)
         pre_start = time.time()
 
-        portal: tractor.Portal = await nursery.start_actor(
+        portal: Portal = await an.start_actor(
             name='aggregator',
             enable_modules=[__name__],
         )
 
-        stream: tractor.MsgStream
+        stream: MsgStream
         async with portal.open_stream_from(
             aggregate,
             seed=seed,
@@ -95,11 +111,12 @@ async def main() -> list[int]:
             start = time.time()
             # the portal call returns exactly what you'd expect
             # as if the remote "aggregate" function was called locally
-            result_stream = []
+            result_stream: list[int] = []
             async for value in stream:
                 result_stream.append(value)
 
-        await portal.cancel_actor()
+        cancelled: bool = await portal.cancel_actor()
+        assert cancelled
 
         print(f"STREAM TIME = {time.time() - start}")
         print(f"STREAM + SPAWN TIME = {time.time() - pre_start}")