Update cwltool/workflow_job.py

Fixed `_completed` attribute type

Co-authored-by: Michael R. Crusoe <[email protected]>

Author: GlassOfWhiskey

cwltool/workflow_job.py

@@ -88,7 +88,7 @@ def __init__(
     ) -> None:
         """Initialize."""
         self.dest = dest
-        self._completed = set()
+        self._completed: Set[int] = set()
         self.processStatus = "success"
         self.total = total
         self.output_callback = output_callback