Why getting firebase is not defined error?

Here's the code for firebase.js file where I m getting this error in spite of strictly adhering to the official documentation of firebase.

Firebase.js

import { initializeApp } from 'firebase/app';
import { getFirestore ,getDocs} from 'https://www.gstatic.com/firebasejs/9.6.3/firebase-firestore.js' 
import { collection} from 'https://www.gstatic.com/firebasejs/9.6.3/firebase-firestore.js' 
// TODO: Add SDKs for Firebase products that you want to use
// https://firebase.google.com/docs/web/setup#available-libraries

// Your web app's Firebase configuration
const firebaseConfig = {
  //config
};

// Initialize Firebase
firebase.initializeApp(firebaseConfig);
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