code: function(validBidRequests, bidderRequest) {
      let ret = {
        method: 'POST',
        url: '',
        data: '',
        bidRequest: []
      };
  
      if (validBidRequests.length < 1) {
        return ret;
      }
  
      // These variables are used in creating the user sync URL.
      siteId = validBidRequests[0].params.siteId;
      bidder = validBidRequests[0].bidder;
  
      const data = Object.assign({
        placements: [],
        time: Date.now(),
        url: utils.getTopWindowUrl(),
        referrer: document.referrer,
        source: [{
          'name': 'prebidjs',
          'version': '$prebid.version$'
        }]
      }, validBidRequests[0].params);
  
      if (bidderRequest && bidderRequest.gdprConsent) {
        data.gdpr = {
          consent: bidderRequest.gdprConsent.consentString,
          applies: (typeof bidderRequest.gdprConsent.gdprApplies === 'boolean') ? bidderRequest.gdprConsent.gdprApplies : true
        };
      }
  
      validBidRequests.map(bid => {
        const placement = Object.assign({
          divName: bid.bidId,
          adTypes: bid.adTypes || getSize(bid.sizes)
        }, bid.params);
  
        if (placement.networkId && placement.siteId && placement.unitId && placement.unitName) {
          data.placements.push(placement);
        }
      });
  
      ret.data = JSON.stringify(data);
      ret.bidRequest = validBidRequests;
      ret.url = BASE_URI;
  
      return ret;
    }
docs: Make a server request from the list of BidRequests.
  
  @param {validBidRequests[]} - an array of bids
  @return ServerRequest Info describing the request to the server.