old_contents: "use strict";
  
  let tags = ;
  
  console.log(`Total items ${tags.size}`);
new_contents: "use strict";
  
  let tags = new Set();
  
  tags.add("JavaScript");
  tags.add("Programming");
  tags.add("Web");
  
  console.log(`Total items ${tags.size}`);
subject: Use Set and methods of Set