docs: function createWantStream (id) {
      if(!streams[id]) {
        streams[id] = notify.listen()
  
        //merge in ids we are pushing.
        var w = clone(want)
        for(var k in push) w[k] = -1
        streams[id].push(w)
      }
      return pull(streams[id], onAbort(function (err, cb) {
        streams[id] = false
        cb(err)
      }))
    }