Added type annotation and comment. (#60)

Author: mtrofin

compiler_opt/distributed/worker.py

@@ -15,7 +15,7 @@
 """Common abstraction for a worker contract."""
 
 import abc
-from typing import Generic, Iterable, TypeVar
+from typing import Generic, Iterable, Optional, TypeVar
 
 
 class Worker:
@@ -50,7 +50,7 @@ def wait_for(futures: Iterable[WorkerFuture]):
       pass
 
 
-def get_exception(worker_future: WorkerFuture):
+def get_exception(worker_future: WorkerFuture) -> Optional[Exception]:
   assert worker_future.done()
   try:
     _ = worker_future.result()

compiler_opt/rl/local_data_collector.py

@@ -54,7 +54,7 @@ def __init__(
     # work completes, i.e. cancelling all work and re-enabling the workers.
     # We remove this activity from the critical path by running it concurrently
     # with the training phase - i.e. whatever happens between successive data
-    # collection calls.
+    # collection calls. Subsequent runs will wait for these to finish.
     self._reset_workers: concurrent.futures.Future = None
     self._current_work: List[Tuple[corpus.ModuleSpec, worker.WorkerFuture]] = []
     self._pool = concurrent.futures.ThreadPoolExecutor()