Invoking configurable_fields method on RunnableConfigurableAlternatives instance throws prefix_keys field required error

[Avinash-Raj]

Checked other resources

• I added a very descriptive title to this issue.
• I searched the LangChain documentation with the integrated search.
• I used the GitHub search to find a similar question and didn't find it.
• I am sure that this is a bug in LangChain rather than my code.

Example Code

from langchain_openai import OpenAI

lm_runnable = (
    OpenAI(temperature=0, openai_api_key="nothing")
    .configurable_alternatives(
        ConfigurableField(id="llm"),
        default_key="openai",
        prefix_keys=False)
    .configurable_fields(
        temperature=ConfigurableField(
            id="llm_temperature",
            name="LLM Temperature",
            description="The temperature of the LLM",
        )
    )
 )  

Error Message and Stack Trace (if applicable)

pydantic.v1.error_wrappers.ValidationError: 1 validation error for RunnableConfigurableAlternatives
prefix_keys
  field required (type=value_error.missing)

Description

I'm trying to add configure_fields to the existing configure_alternatives instance but I got the below exception.

System Info

langchain==0.1.8
langchain-community==0.0.21
langchain-core==0.1.25
langchain-openai==0.0.6