agrego posibilidad de elegir del LLM modelo de OPENAI

app.py

@@ -14,6 +14,8 @@ st.header("Hacele preguntal al doc PDF que cargues")
 OPENAI_API_KEY = st.text_input('OpenAI API Key', type='password')
 pdf_obj = st.file_uploader("Cargá el documento", type="pdf", on_change=st.cache_resource.clear)
 
+model = st.selectbox("Model",("gpt-3.5-turbo","gpt-4","gpt-4.5-preview"))
+
 @st.cache_resource 
 def create_embeddings(pdf):
     pdf_reader = PdfReader(pdf)
@@ -40,7 +42,7 @@ if pdf_obj:
     if user_question:
         os.environ["OPENAI_API_KEY"] = OPENAI_API_KEY
         docs = knowledge_base.similarity_search(user_question, 3)
-        llm = ChatOpenAI(model_name='gpt-4.5-preview')
+        llm = ChatOpenAI(model_name=model)#llm = ChatOpenAI(model_name='gpt-4.5-preview')
         chain = load_qa_chain(llm, chain_type="stuff")
         respuesta = chain.run(input_documents=docs, question=user_question)