I can't use Vue.toast.show('Welcome!', 'Hey')

[Razor7w]

Describe the bug
I try use library in external js, export all:

import VueIziToast from 'vue-izitoast'
import 'izitoast/dist/css/iziToast.min.css'
Vue.use(VueIziToast)

and when I want to use

Vue.toast.show('Welcome!', 'Hey')

shows on the console

Uncaught (in promise) TypeError: Cannot read property 'show' of undefined
    at eval (izitoast.js?57fa:29)
    at eval (vuex.esm.js?2f62:468)
    at Array.forEach (<anonymous>)
    at Store.commit (vuex.esm.js?2f62:468)
    at Store.boundCommit [as commit] (vuex.esm.js?2f62:405)
    at local.commit (vuex.esm.js?2f62:792)
    at eval (actions.js?43b5:36)
    at <anonymous>

Additional context
Use js external to vue, i cant use this.$toast.show('Welcome!', 'Hey') in this file