code: function getHeaders(id) {
          var bucket = options.getBucket(id),
              host = options.getHost(id),
              headers = {},
              promise = new qq.Promise(),
              key = options.getKey(id),
              signatureConstructor;
  
          headers["x-amz-acl"] = options.aclStore.get(id);
  
          if (options.reducedRedundancy) {
              headers[qq.s3.util.REDUCED_REDUNDANCY_PARAM_NAME] = qq.s3.util.REDUCED_REDUNDANCY_PARAM_VALUE;
          }
  
          if (options.serverSideEncryption) {
              headers[qq.s3.util.SERVER_SIDE_ENCRYPTION_PARAM_NAME] = qq.s3.util.SERVER_SIDE_ENCRYPTION_PARAM_VALUE;
          }
  
          headers[qq.s3.util.AWS_PARAM_PREFIX + options.filenameParam] = encodeURIComponent(options.getName(id));
  
          qq.each(options.paramsStore.get(id), function(name, val) {
              if (qq.indexOf(qq.s3.util.UNPREFIXED_PARAM_NAMES, name) >= 0) {
                  headers[name] = val;
              }
              else {
                  headers[qq.s3.util.AWS_PARAM_PREFIX + name] = encodeURIComponent(val);
              }
          });
  
          signatureConstructor = getSignatureAjaxRequester.constructStringToSign
              (getSignatureAjaxRequester.REQUEST_TYPE.MULTIPART_INITIATE, bucket, host, key)
              .withContentType(options.getContentType(id))
              .withHeaders(headers);
  
          // Ask the local server to sign the request.  Use this signature to form the Authorization header.
          getSignatureAjaxRequester.getSignature(id, {signatureConstructor: signatureConstructor}).then(promise.success, promise.failure);
  
          return promise;
      }
docs: Determine all headers for the "Initiate MPU" request, including the "Authorization" header, which must be determined
  by the local server.  This is a promissory function.  If the server responds with a signature, the headers
  (including the Authorization header) will be passed into the success method of the promise.  Otherwise, the failure
  method on the promise will be called.
  
  @param id Associated file ID
  @returns {qq.Promise}