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Signed-off-by: Kai-Hsun Chen <kaihsun@anyscale.com>

Author: kevin85421

python/ray/dag/dag_node.py

@@ -75,7 +75,13 @@ def __init__(
         self.is_output_node = False
 
     def _prepare_upstream_nodes(self) -> List["DAGNode"]:
-        """Retrieve upstream nodes and update their downstream dependencies."""
+        """
+        Retrieve upstream nodes and update their downstream dependencies.
+
+        TODO (kevin85421): Currently, the upstream nodes and downstream nodes have
+        circular references. Therefore, it relies on the garbage collector to clean
+        them up.
+        """
         scanner = _PyObjScanner()
         upstream_nodes: List["DAGNode"] = scanner.find_nodes(
             [

python/ray/dag/tests/experimental/test_accelerated_dag.py

@@ -1186,6 +1186,11 @@ def test_leaf_node_two_actors(self, ray_start_regular):
 
 
 def test_output_node(ray_start_regular):
+    """
+    This test is similar to the `test_output_node` in `test_output_node.py`, but
+    this test is for the accelerated DAG.
+    """
+
     @ray.remote
     class Worker:
         def __init__(self):