code: function getUserSyncs (syncOptions, serverResponses) {
    const responses = serverResponses.map((response) => {
      return (response.body && response.body.pxs && response.body.pxs.scr) || []
    })
    const userSyncs = responses.reduce(function (usersyncs, response) {
      return usersyncs.concat(response)
    }, [])
    const syncs = userSyncs.map((sync) => {
      return {
        type: sync.t === 'f' ? 'iframe' : 'image',
        url: sync.u
      }
    })
    return syncs;
  }
docs: Register the user sync pixels which should be dropped after the auction.
  
  @param {SyncOptions} syncOptions Which user syncs are allowed?
  @param {ServerResponse[]} serverResponses List of server's responses.
  @return {UserSync[]} The user syncs which should be dropped.