How can I add a function to the plugin?

[Rasool-deldar]

I want to add a function to checkPermission to the plugin to get access level How can I enable this now that I can create a plugin but it gives an error.

import { defineNuxtPlugin } from '@nuxtjs/composition-api';

// @ts-ignore
// eslint-disable-next-line @typescript-eslint/no-unused-vars
export default defineNuxtPlugin(({ $auth, redirect }) => {
  // @ts-ignore
  // eslint-disable-next-line no-param-reassign,@typescript-eslint/no-unused-vars
  $auth.checkPermission = (permission: string = 'index') => {
    console.log($auth.user.full_name);
  };
});