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from langchain.chains import LLMChain
from langchain.output_parsers import PydanticOutputParser
from langchain.prompts import PromptTemplate
from pydantic import BaseModel, Field

query = "Do you offer vegetarian food?"

class LineList(BaseModel):
    lines: list[str] = Field(description="Lines of text")


class LineListOutputParser(PydanticOutputParser):
    def __init__(self) -> None:
        super().__init__(pydantic_object=LineList)

    def parse(self, text: str) -> list[str]:
        lines = text.strip().split("\n")
        return lines


output_parser = LineListOutputParser()

QUERY_PROMPT = PromptTemplate(
    input_variables=["question"],
    template="""You are an AI language model assistant. Your task is to generate five
    different versions of the given user question to retrieve relevant documents from a vector
    database. By generating multiple perspectives on the user question, your goal is to help
    the user overcome some of the limitations of the distance-based similarity search.
    Provide these alternative questions separated by newlines. Only provide the query, no numbering.
    Original question: {question}""",
)

llm_chain = LLMChain(llm=llm, prompt=QUERY_PROMPT, output_parser=output_parser)
queries = llm_chain.invoke(query)

{
	"name": "ValidationError",
	"message": "1 validation error for LineListOutputParser
pydantic_object
  subclass of BaseModel expected (type=type_error.subclass; expected_class=BaseModel)",
	"stack": "---------------------------------------------------------------------------
ValidationError                           Traceback (most recent call last)
Cell In[23], line 21
     17         lines = text.strip().split(\"\
\")
     18         return lines
---> 21 output_parser = LineListOutputParser()
     23 QUERY_PROMPT = PromptTemplate(
     24     input_variables=[\"question\"],
     25     template=\"\"\"You are an AI language model assistant. Your task is to generate five
   (...)
     30     Original question: {question}\"\"\",
     31 )
     33 llm_chain = LLMChain(llm=llm, prompt=QUERY_PROMPT, output_parser=output_parser)

Cell In[23], line 14, in LineListOutputParser.__init__(self)
     13 def __init__(self) -> None:
---> 14     super().__init__(pydantic_object=LineList)

File ~/.local/lib/python3.10/site-packages/langchain_core/load/serializable.py:107, in Serializable.__init__(self, **kwargs)
    106 def __init__(self, **kwargs: Any) -> None:
--> 107     super().__init__(**kwargs)
    108     self._lc_kwargs = kwargs

File ~/.local/lib/python3.10/site-packages/pydantic/v1/main.py:341, in BaseModel.__init__(__pydantic_self__, **data)
    339 values, fields_set, validation_error = validate_model(__pydantic_self__.__class__, data)
    340 if validation_error:
--> 341     raise validation_error
    342 try:
    343     object_setattr(__pydantic_self__, '__dict__', values)

ValidationError: 1 validation error for LineListOutputParser
pydantic_object
  subclass of BaseModel expected (type=type_error.subclass; expected_class=BaseModel)"
}