Microsoft.Azure.WebJobs.Host: Unable to resolve the value for property 'SendGridAttribute.ApiKe y'. Make sure the setting exists and has a valid value.

[Sanketbhangale]

I am using azure/functions version 4.0.1. Which we recently updated from version 3.
So we removed the function.json and registered our functions like below:

import { processor } from "./processor";

import { app, output } from "@azure/functions";

const queueName = config.loadString("AZURE_SERVICEBUS_EMAIL_QUEUE_NAME");
const sendGridApiKey = config.loadString("SENDGRID_API_KEY");

app.serviceBusQueue("EmailSendingFunction", {
    connection: "AZURE_SERVICEBUS_CONNECTION_STRING",
    queueName,
    handler: processor,
    return: output.generic({
        type: "sendGrid",
        apiKey: sendGridApiKey,
    }),
});

export default processor;

But we get an error:

System.Private.CoreLib: Exception while executing function: Functions.EmailSendingFunction. Microsoft.Azure.WebJobs.Host: Unable to resolve the value for property 'SendGridAttribute.ApiKe
y'. Make sure the setting exists and has a valid value.

Please provide a resolution as there is no documentation on how the sendGrid output binding works in v4.