test: tighten prepare_key_update_data mock and apply black

- test_prepare_key_update_data: replace bare MagicMock with
  MagicMock(spec=LiteLLM_VerificationToken) and explicitly set
  existing_key_row.metadata = {}, so reserved-field reads return real
  values instead of MagicMock-returning-MagicMock. Fixes a regression
  surfaced by the new reserved-metadata preservation logic.
- test_key_management_endpoints.py: black-format-only changes from
  recent edits.

tests/proxy_unit_tests/test_proxy_utils.py

@@ -686,12 +686,13 @@ async def test_proxy_config_update_from_db():
 
 @pytest.mark.asyncio
 async def test_prepare_key_update_data():
-    from litellm.proxy._types import UpdateKeyRequest
+    from litellm.proxy._types import LiteLLM_VerificationToken, UpdateKeyRequest
     from litellm.proxy.management_endpoints.key_management_endpoints import (
         prepare_key_update_data,
     )
 
-    existing_key_row = MagicMock()
+    existing_key_row = MagicMock(spec=LiteLLM_VerificationToken)
+    existing_key_row.metadata = {}
     data = UpdateKeyRequest(key="test_key", models=["gpt-4"], duration="120s")
     updated_data = await prepare_key_update_data(data, existing_key_row)
     assert "expires" in updated_data

tests/test_litellm/proxy/management_endpoints/test_key_management_endpoints.py

@@ -1229,9 +1229,7 @@ async def test_update_preserves_service_account_id_when_metadata_replaced():
         metadata={"service_account_id": "sa-123"},
     )
 
-    result = await prepare_key_update_data(
-        data=data, existing_key_row=existing_key
-    )
+    result = await prepare_key_update_data(data=data, existing_key_row=existing_key)
 
     assert result["metadata"]["service_account_id"] == "sa-123"
     assert result["metadata"]["unrelated"] == "value"
@@ -1274,9 +1272,7 @@ async def test_update_allows_matching_service_account_id():
         metadata={"service_account_id": "sa-123"},
     )
 
-    result = await prepare_key_update_data(
-        data=data, existing_key_row=existing_key
-    )
+    result = await prepare_key_update_data(data=data, existing_key_row=existing_key)
 
     assert result["metadata"]["service_account_id"] == "sa-123"
     assert result["metadata"]["other"] == "value"
@@ -1334,9 +1330,7 @@ async def test_update_without_metadata_still_preserves_existing():
         metadata={"service_account_id": "sa-123", "other": "kept"},
     )
 
-    result = await prepare_key_update_data(
-        data=data, existing_key_row=existing_key
-    )
+    result = await prepare_key_update_data(data=data, existing_key_row=existing_key)
 
     assert result["metadata"]["service_account_id"] == "sa-123"
     assert result["metadata"]["other"] == "kept"
@@ -8221,9 +8215,7 @@ async def test_update_key_non_budget_rejects_cross_user_modification(monkeypatch
     )
 
     mock_prisma_client = AsyncMock()
-    test_hashed_token = (
-        "cafebabe" * 8
-    )
+    test_hashed_token = "cafebabe" * 8
 
     mock_existing_key = MagicMock()
     mock_existing_key.token = test_hashed_token