Make Safety test work, other cleanup

llama_stack/providers/impls/meta_reference/safety/safety.py

@@ -12,6 +12,8 @@ from llama_stack.apis.safety import *  # noqa: F403
 from llama_models.llama3.api.datatypes import *  # noqa: F403
 from llama_stack.distribution.datatypes import Api
 
+from llama_stack.providers.datatypes import ShieldsProtocolPrivate
+
 from .base import OnViolationAction, ShieldBase
 from .config import SafetyConfig
 from .llama_guard import LlamaGuardShield
@@ -21,7 +23,7 @@ from .prompt_guard import InjectionShield, JailbreakShield, PromptGuardShield
 PROMPT_GUARD_MODEL = "Prompt-Guard-86M"
 
 
-class MetaReferenceSafetyImpl(Safety):
+class MetaReferenceSafetyImpl(Safety, ShieldsProtocolPrivate):
     def __init__(self, config: SafetyConfig, deps) -> None:
         self.config = config
         self.inference_api = deps[Api.inference]
@@ -41,8 +43,17 @@ class MetaReferenceSafetyImpl(Safety):
         pass
 
     async def register_shield(self, shield: ShieldDef) -> None:
-        if shield.type not in self.available_shields:
-            raise ValueError(f"Unsupported safety shield type: {shield.type}")
+        raise ValueError("Registering dynamic shields is not supported")
+
+    async def list_shields(self) -> List[ShieldDef]:
+        return [
+            ShieldDef(
+                identifier=shield_type,
+                type=shield_type,
+                params={},
+            )
+            for shield_type in self.available_shields
+        ]
 
     async def run_shield(
         self,