redux-devtools/packages/redux-devtools-trace-monitor/.babelrc

{
  "presets": [
    "@babel/preset-env", "@babel/preset-react", "@babel/preset-flow"
  ],
  "plugins": [
    ["@babel/plugin-transform-runtime", {
      "regenerator": true
    }],
    [
      "@babel/plugin-proposal-decorators",
      { "legacy": true }
    ],
    "@babel/plugin-proposal-class-properties"
  ]
}