fix punctuation error in comment

b_asic/operation.py

@@ -88,7 +88,7 @@ class Operation(GraphComponent):
     @abstractmethod
     def neighbors(self) -> "List[Operation]":
         """Return all operations that are connected by signals to this operation.
-        If no neighbors are found this returns an empty list
+        If no neighbors are found, this returns an empty list.
         """
         raise NotImplementedError