docs: function yarn(cmds, args, cb) {
    if (typeof args === 'function') {
      return yarn(cmds, [], args);
    }
  
    args = arrayify(cmds).concat(arrayify(args));
    spawn('yarn', args, {cwd: cwd, stdio: 'inherit'})
      .on('error', cb)
      .on('close', function(code, err) {
        cb(err, code);
      });
  }