langchain[major]: Remove default instantations of LLMs from VectorstoreToolkit (#20794)

Remove default instantiation from vectorstore toolkit.

libs/langchain/langchain/agents/agent_toolkits/vectorstore/toolkit.py

@@ -8,10 +8,9 @@ from langchain_community.tools.vectorstore.tool import (
 )
 from langchain_core.language_models import BaseLanguageModel
 from langchain_core.pydantic_v1 import BaseModel, Field
+from langchain_core.tools import BaseTool
 from langchain_core.vectorstores import VectorStore
 
-from langchain.tools import BaseTool
-
 
 class VectorStoreInfo(BaseModel):
     """Information about a VectorStore."""

libs/langchain/langchain/chains/flare/base.py

@@ -5,7 +5,6 @@ from abc import abstractmethod
 from typing import Any, Dict, List, Optional, Sequence, Tuple
 
 import numpy as np
-from langchain_community.llms.openai import OpenAI
 from langchain_core.callbacks import (
     CallbackManagerForChainRun,
 )
@@ -56,11 +55,7 @@ class _ResponseChain(LLMChain):
 class _OpenAIResponseChain(_ResponseChain):
     """Chain that generates responses from user input and context."""
 
-    llm: OpenAI = Field(
-        default_factory=lambda: OpenAI(
-            max_tokens=32, model_kwargs={"logprobs": 1}, temperature=0
-        )
-    )
+    llm: BaseLanguageModel
 
     def _extract_tokens_and_log_probs(
         self, generations: List[Generation]
@@ -118,7 +113,7 @@ class FlareChain(Chain):
 
     question_generator_chain: QuestionGeneratorChain
     """Chain that generates questions from uncertain spans."""
-    response_chain: _ResponseChain = Field(default_factory=_OpenAIResponseChain)
+    response_chain: _ResponseChain
     """Chain that generates responses from user input and context."""
     output_parser: FinishedOutputParser = Field(default_factory=FinishedOutputParser)
     """Parser that determines whether the chain is finished."""
@@ -255,6 +250,14 @@ class FlareChain(Chain):
         Returns:
             FlareChain class with the given language model.
         """
+        try:
+            from langchain_openai import OpenAI
+        except ImportError:
+            raise ImportError(
+                "OpenAI is required for FlareChain. "
+                "Please install langchain-openai."
+                "pip install langchain-openai"
+            )
         question_gen_chain = QuestionGeneratorChain(llm=llm)
         response_llm = OpenAI(
             max_tokens=max_generation_len, model_kwargs={"logprobs": 1}, temperature=0