code: func NewPEXReactor(b *AddrBook) *PEXReactor {
  	r := &PEXReactor{
  		book:              b,
  		ensurePeersPeriod: defaultEnsurePeersPeriod,
  		msgCountByPeer:    cmn.NewCMap(),
  		maxMsgCountByPeer: defaultMaxMsgCountByPeer,
  	}
  	r.BaseReactor = *NewBaseReactor(log, "PEXReactor", r)
  	return r
  }
docs: // NewPEXReactor creates new PEX reactor.