[Placement group] Check if placement group bundle index is valid (#10194)

* add part code

* rebase master

* add java testcase

* fix review comments

* fix lint error

* rebase master

* fix lint error

Co-authored-by: 灵洵 <fengbin.ffb@antfin.com>

python/ray/experimental/placement_group.py

@@ -1,8 +1,15 @@
 from typing import (List, Dict)
 
 import ray
-from ray._raylet import (
-    PlacementGroupID, )
+
+
+class PlacementGroup:
+    """A handle to a placement group.
+    """
+
+    def __init__(self, id, bundle_count):
+        self.id = id
+        self.bundle_count = bundle_count
 
 
 def placement_group(bundles: List[Dict[str, float]],
@@ -33,19 +40,32 @@ def placement_group(bundles: List[Dict[str, float]],
     placement_group_id = worker.core_worker.create_placement_group(
         name, bundles, strategy)
 
-    return placement_group_id
+    return PlacementGroup(placement_group_id, len(bundles))
 
 
-def remove_placement_group(placement_group_id: PlacementGroupID):
-    assert type(placement_group_id) == PlacementGroupID
+def remove_placement_group(placement_group):
+    assert placement_group is not None
     worker = ray.worker.global_worker
     worker.check_connected()
 
-    worker.core_worker.remove_placement_group(placement_group_id)
+    worker.core_worker.remove_placement_group(placement_group.id)
 
 
-def placement_group_table(placement_group_id):
-    assert placement_group_id is not None
+def placement_group_table(placement_group):
+    assert placement_group is not None
     worker = ray.worker.global_worker
     worker.check_connected()
-    return ray.state.state.placement_group_table(placement_group_id)
+    return ray.state.state.placement_group_table(placement_group.id)
+
+
+def check_placement_group_index(placement_group, bundle_index):
+    assert placement_group is not None
+    if placement_group.id.is_nil():
+        if bundle_index != -1:
+            raise ValueError("If placement group is not set, "
+                             "the value of bundle index must be -1.")
+    elif bundle_index >= placement_group.bundle_count \
+            or bundle_index < -1:
+        raise ValueError(f"placement group bundle index {bundle_index} "
+                         f"is invalid. Valid placement group indexes: "
+                         f"0-{placement_group.bundle_count}")