Fix missing and unused imports in custom_guardrail docs example

docs/my-website/docs/proxy/guardrails/custom_guardrail.md

@@ -23,15 +23,14 @@ A CustomGuardrail has 4 methods to enforce guardrails
 
 Create a new file called `custom_guardrail.py` and add this code to it
 ```python
-from typing import Any, Dict, List, Literal, Optional, Union
+from typing import Any, AsyncGenerator, Literal, Optional, Union
 
 import litellm
 from litellm._logging import verbose_proxy_logger
 from litellm.caching.caching import DualCache
 from litellm.integrations.custom_guardrail import CustomGuardrail
 from litellm.proxy._types import UserAPIKeyAuth
-from litellm.proxy.guardrails.guardrail_helpers import should_proceed_based_on_metadata
-from litellm.types.guardrails import GuardrailEventHooks
+from litellm.types.utils import ModelResponseStream
 
 
 class myCustomGuardrail(CustomGuardrail):