fixed a dependency duplicate (#15444)

BaseModel is derived twice. Left only one.

libs/langchain/langchain/retrievers/self_query/base.py

@@ -21,7 +21,7 @@ from langchain_community.vectorstores import (
 )
 from langchain_core.documents import Document
 from langchain_core.language_models import BaseLanguageModel
-from langchain_core.pydantic_v1 import BaseModel, Field, root_validator
+from langchain_core.pydantic_v1 import Field, root_validator
 from langchain_core.retrievers import BaseRetriever
 from langchain_core.runnables import Runnable
 from langchain_core.vectorstores import VectorStore
@@ -85,7 +85,7 @@ def _get_builtin_translator(vectorstore: VectorStore) -> Visitor:
         )
 
 
-class SelfQueryRetriever(BaseRetriever, BaseModel):
+class SelfQueryRetriever(BaseRetriever):
     """Retriever that uses a vector store and an LLM to generate
     the vector store queries."""