old_contents: const agents = require('caniuse-db/data.json').agents;
  
  Object.keys(agents).forEach(function (key) {
      var browser = agents[key];
      browser.versions = browser.versions.filter(Boolean);
  });
  
  module.exports = agents;
  
new_contents: var agents = require('caniuse-db/data.json').agents;
  
  Object.keys(agents).forEach(function (key) {
      var browser = agents[key];
      browser.versions = browser.versions.filter(Boolean);
  });
  
  module.exports = agents;
  
subject: Remove ES6