https://python.langchain.com/v0.2/docs/versions/v0_2/deprecations/#llmchain

Encontrei a resposta.

%pip install --upgrade --quiet  langchain langchain-openai

from langchain_core.output_parsers import StrOutputParser
from langchain_core.prompts import ChatPromptTemplate
from langchain_core.runnables import chain
from langchain_openai import ChatOpenAI

prompt1 = ChatPromptTemplate.from_template("Tell me a joke about {topic}")
prompt2 = ChatPromptTemplate.from_template("What is the subject of this joke: {joke}")

@chain
def custom_chain(text):
    prompt_val1 = prompt1.invoke({"topic": text})
    output1 = ChatOpenAI().invoke(prompt_val1)
    parsed_output1 = StrOutputParser().invoke(output1)
    chain2 = prompt2 | ChatOpenAI() | StrOutputParser()
    return chain2.invoke({"joke": parsed_output1})

custom_chain.invoke("bears")

'The subject of this joke is bears.'

Oii, Wilson! Tudo bem?

Fico feliz que tenha encontrado a solução para a dúvida que estava tendo. Continue se dedicando aos estudos e praticando os exercícios.

Qualquer dúvida, compartilhe conosco para podermos te auxiliar.

Abraço!