text: Title: AttributeError: 'LangchainLLM' object has no attribute '_llm_type'
  Body: ### System Info
  
  pandasai==3.0.0b14
  system in windows10 and ubuntu22.04
  python3.11
  
  ### 🐛 Describe the bug
  
  from langchain.chat_models import ChatOpenAI
  import pandasai as pai
  from pandasai_langchain import LangchainLLM
  
  dataset_path = "qshop/log-data"
  try:
      sql_table = pai.create(
          path=dataset_path,
          description="XXXXXXXXXXXXXX",
          source={
              "type": "mysql",
              "connection": {
                  "host": "192.168.0.4",
                  "port": 8096,
                  "user": "qshop_rw",
                  "password": "Hd43eN+DkNaR",
                  "database": "qshop"
              },
              "table": "tb_log"
          },        
          columns=[
              {
                  "name": "Id",
                  "type": "string",
                  "description": "每条数据的唯一标识符"
              },
              {
                  "name": "UserID",
                  "type": "string",
                  "description": "此条操作记录的用户，无就代表用户没登录"
              },
              {
                  "name": "CreateTime",
                  "type": "datetime",
                  "description": "此条操作记录的产生的时间"
              },
              {
                  "name": "PageName",
                  "type": "string",
                  "description": "此条操作记录访问的页面名称"
              },
              {
                  "name": "GoodsName",
                  "type": "string",
                  "description": "此条操作记录访问的产品的名称，或者需求的名称，或者视频资讯的名称"
              },
              {
                  "name": "Col1",
                  "type": "string",
                  "description": "辅助判断列，如果值为小模型发布则说明GoodsName对应的是产品，如果值为小模型需求则说明GoodsName对应的是需求，如果值为小模型视频说明GoodsName对应的是视频资讯"
              }
          ]
      )
      print(f"成功创建新数据集: {dataset_path}")
  except Exception as e:
      print(f"创建数据集时出错: {e}")
  
  
  llm = ChatOpenAI(base_url='https://XXXX.XXX.XX.XX:XXX/v1/',
                   api_key='sk-proj-1234567890',
                   model='deepseek-r1-distill-qwen',
                   request_timeout=300)
  llm1 = LangchainLLM(langchain_llm=llm)
  pai.config.set({
      "llm": llm1,
      "timeout": 300,
      "enable_cache": False,
  })
  # 从连接器获取数据
  agent = pai.load('qshop/log-data')
  # 示例查询
  ans = agent.chat("请根据这个表格生成一份访问分析报告，并根据报告给出后续的运营建议。")
  print(ans)
  Exception has occurred: AttributeError
  'LangchainLLM' object has no attribute '_llm_type'
    File "E:\develop\aiagent\pandasaitest.py", line 84, in <module>
      ans = agent.chat("请根据这个表格生成一份访问分析报告，并根据报告给出后续的运营建议。")
            ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  AttributeError: 'LangchainLLM' object has no attribute '_llm_type'
  