text: define(function (require) {
    return function FetchMergeDuplicateRequests(Private) {
      var isRequest = Private(require('components/courier/fetch/_is_request'));
      var DUPLICATE = Private(require('components/courier/fetch/_req_status')).DUPLICATE;
  
      function mergeDuplicateRequests(requests) {
        // dedupe requests
        var index = {};
        return requests.map(function (req) {
          if (!isRequest(req)) return req;
  
          var iid = req.source._instanceid;
          if (!index[iid]) {
            // this request is unique so far
            index[iid] = req;
            // keep the request
            return req;
          }
  
          // the source was requested at least twice
          req._uniq = index[iid];
          return DUPLICATE;
        });
      }
  
      return mergeDuplicateRequests;
    };
  });