Remove/exclude default response from langserve chain response while invoke method curl or postman with Pydantic Output Parser

Question

In Langserve API, created below route
eg: http://localhost:8000/get_gpt4/invoke

app = FastAPI(title=" API",
    version="1.0",
    description="Helper APIs to augment language models"
)
add_routes(
    app,
    PredictCustomOutput(),
    path="/get_gpt4",
)

in xyz.py

from langchain_core.output_parsers import JsonOutputParser
from langchain_core.pydantic_v1 import BaseModel, Field

class Classify(BaseModel):
    Prediction: str = Field(description="predict text")
    Explanation: str = Field(description="predicted explanation text")

def PredictCustomOutput() -> Runnable:
    """ Return chain """
    model = get_ChatOpenAI(model_name="azure-openai")
    template = get_prompt_template(name="gpt4_ae_classify_finetune")
    parser = JsonOutputParser(pydantic_object=Classify)

    prompt = PromptTemplate(
        template=template+"\n{format_instructions}\n{text}\n",
        input_variables=["text"],
        partial_variables={"format_instructions": parser.get_format_instructions()},

    )
    chain = prompt | model | parser
    return chain

While invoking the API from postman or FastAPI, I was expecting to receive the following response output:

{ 
    "Prediction": "Event",
    "Explanation": "description of predict "
}

but instead, I'm getting the response below:

{
    "output": {
               "Prediction": "Event",
               "Explanation": "description of predict "

    },
    "callback_events": [],
    "metadata": {
        "run_id": "14f4a9a8-f3a8-4773-a29a-6d445c4a1ac8"
    }
}

Output parser I was trying this on Notebook, but I want to get a response from the API in this format:

{ 
"Prediction": "Event",
"Explanation": "description of predict "
}