update var name

wren-ai-service/src/providers/llm/openai.py

@@ -60,23 +60,23 @@ def __init__(
         )
 
         # check if the model is actually Vertex AI model
-        self.vertexai_creds = None
+        self._vertexai_creds = None
         if model.startswith("google/"):
-            self.vertexai_creds, _ = google.auth.default(
+            self._vertexai_creds, _ = google.auth.default(
                 scopes=["https://www.googleapis.com/auth/cloud-platform"]
             )
 
     def __getattr__(self, name: str) -> Any:
         # dealing with auto-refreshing expired credential
         # https://cloud.google.com/vertex-ai/generative-ai/docs/multimodal/call-vertex-using-openai-library#refresh_your_credentials
-        if self.vertexai_creds and not self.vertexai_creds.valid:
+        if self._vertexai_creds and not self._vertexai_creds.valid:
             auth_req = google.auth.transport.requests.Request()
-            self.vertexai_creds.refresh(auth_req)
+            self._vertexai_creds.refresh(auth_req)
 
-            if not self.vertexai_creds.valid:
+            if not self._vertexai_creds.valid:
                 raise RuntimeError("Unable to refresh auth")
 
-            self.client.api_key = self.vertexai_creds.token
+            self.client.api_key = self._vertexai_creds.token
         return getattr(self.client, name)
 
     @component.output_types(replies=List[str], meta=List[Dict[str, Any]])