`LangchainPredict` class not compatible with `COPRO` optimizer

[aishwaryap]

Although this is included in this more general issue outlining issues with integration with Langchain, it felt beneficial to create a new issue for this particular error. With the latest dspy-ai==2.4.13, the Langchain integration example runs but if the optimizer in the notebook is changed to COPRO, it fails with the following error:

---------------------------------------------------------------------------
AttributeError                            Traceback (most recent call last)
Cell In[12], line 4
      2 teleprompter = COPRO(prompt_model=llm, metric=metric)
      3 kwargs = dict(num_threads=8, display_progress=True, display_table=0)
----> 4 compiled_prompt_opt = teleprompter.compile(zeroshot_chain, trainset=trainset, eval_kwargs=kwargs)
      5 eval_score = evaluate(compiled_prompt_opt, devset=testset, **kwargs)

File [~/Documents/venvs/dspy_v3_env/lib/python3.10/site-packages/dspy/teleprompt/copro_optimizer.py:160](http://localhost:8888/lab/tree/~/Documents/venvs/dspy_v3_env/lib/python3.10/site-packages/dspy/teleprompt/copro_optimizer.py#line=159), in COPRO.compile(self, student, trainset, eval_kwargs)
    158 basic_instruction = None
    159 basic_prefix = None
--> 160 *_, last_key = self._get_signature(predictor).fields.keys()
    161 basic_instruction = self._get_signature(predictor).instructions
    162 basic_prefix = self._get_signature(predictor).fields[last_key].json_schema_extra["prefix"]

AttributeError: 'list' object has no attribute 'keys'

[arnavsinghvi11]

Hi @aishwaryap , most of the community-integrated modules like Langchain, Llamaindex, etc. were not built in concert with some of the new optimizers and will need some implementation details refined/updated. Particularly, this sets up the signature using the Langchain template, while DSPy module signatures use DSPy templates, which is why the error is triggered. Will keep this issue open for further investigation and/or if members using Langchain have suggestions for better integration of the Langchain modules to ensure this compatibility.

Additionally, I recommend using MIPROv2 over COPRO going forward!

[okhat]

Consider Zenbase @CyrusOfEden for LangChain<>DSPy integrations, @aishwaryap !