I am building a library to be used to call api's

I am using rollup to bundle all the files into one file, the issue is its adding this line

import util from 'util';

not sure what it does, I am not using anything from util

below is my rollup config file

import nodeGlobals from "rollup-plugin-node-globals";
import commonjs from "rollup-plugin-commonjs";
import uglify from "rollup-plugin-uglify";
import babel from "rollup-plugin-babel";
import replace from "rollup-plugin-replace";
import resolve from "rollup-plugin-node-resolve";
import rollupJson from "rollup-plugin-json";

export default [
    {
        input: 'src/config.js',
        output: [
            {
                name:"asd",
                file: 'dist/bundle-b2.js',
                format: 'es',
            }
        ],
        plugins: [
            babel({
                babelrc: false,
                presets: [
                    ["airbnb",{"modules":false}],
                    ["env",{"modules":false,"useBuiltIns": false}],
                    ["es2015",{"modules":false}],
                    ['stage-2']],
                exclude:[
                    'node_modules/**',
                ],
                plugins: ['external-helpers', ["transform-builtin-extend", {
                    globals: ["Error", "Array"],
                }]],
                externalHelpers: true,
                runtimeHelpers: true,

            }),
            resolve({
                jsnext: true,
                preferBuiltins: true,
                browser: true,
            }),
            commonjs({
                include: 'node_modules/**'
            }),
            nodeGlobals(
                {
                    process:true,
                    global:false,
                    Buffer:false
                }
            ),

            rollupJson({compact: true
            }),

            replace({
                'process.env.NODE_ENV': JSON.stringify('production'),
            }),
        ]
    }
];

any help please ?

Thanks