code: async function build(inputOptions, outputOptions) {
    const input = Object.assign(
      {
        plugins: [
          commonjs(), // We can remove this plugin if there are no more CommonJS modules
          resolve(), // We need this plugin only to build the test script
          babel({
            exclude: 'node_modules/**'
          })
        ]
      },
      inputOptions
    );
  
    const output = Object.assign(
      {
        format: 'umd'
      },
      outputOptions
    );
  
    const bundle = await rollup(input);
    await bundle.write(output);
  }
docs: Only needed for test build 
  Build using rollup.js
  
  @see https://rollupjs.org/#javascript-api
  
  @param inputOptions
  @param outputOptions
  @returns Promise