[docs] redirect with fixed ci fails - langchain (#3699)

mem0/vector_stores/vertex_ai_vector_search.py

@@ -5,13 +5,15 @@ from typing import Any, Dict, List, Optional, Tuple
 
 import google.api_core.exceptions
 from google.cloud import aiplatform, aiplatform_v1
-from google.cloud.aiplatform.matching_engine.matching_engine_index_endpoint import (
-    Namespace,
-)
+from google.cloud.aiplatform.matching_engine.matching_engine_index_endpoint import Namespace
 from google.oauth2 import service_account
-from langchain.schema import Document
 from pydantic import BaseModel
 
+try:
+    from langchain_core.documents import Document
+except ImportError:  # pragma: no cover - fallback for older LangChain versions
+    from langchain.schema import Document  # type: ignore[no-redef]
+
 from mem0.configs.vector_stores.vertex_ai_vector_search import (
     GoogleMatchingEngineConfig,
 )