Failed to load function definition from source: Failed to generate manifest from function source

Question

I am trying to deploy the following code in firebase function but getting the following error :

Error: Failed to load function definition from source: Failed to generate manifest from function source: Error: Counter already defined for field "notification_id"

When removing the notification_id the deployment is taking place successfully but as soon as I add notification_id it shows the error.

If someone can please help me resolve this issue.

node.js

const mongoose = require('mongoose');
const AutoIncrement = require('mongoose-sequence')(mongoose);

const userProjectSurveySchema = new mongoose.Schema({
    userId: 
    {
        type: Number,
        required: true,
        trim: true
    },
    notification_id: 
    {
        type: Number,
    },
    notification_type: 
    {
        type: Number,
        required: true,
       
    },
    status: 
    {       
         type: String,
         required: true
    },

    questions: [
        {
            qn: {
            type: String,
            required: true
        },
        options: [
            { 
                option: {
                    type: String
                },
                totalViews: {
                    type:Number
                }

             } 
    ]    
    },
    ],
    created_at:  {       
    type: Date,
    required: true,
    default: Date.now(),
},
   
});

userProjectSurveySchema.plugin(AutoIncrement, {inc_field: 'notification_id'});


module.exports = mongoose.model('UserProjectSurveyDetails', userProjectSurveySchema);