code: func (r *Registry) createPriceOracle() {
  	sp := &StreamerPrices{
  		registry: r,
  	}
  	sp.priceMatrix = map[reflect.Type]*protocols.Price{
  		reflect.TypeOf(ChunkDeliveryMsgRetrieval{}): {
  			Value:   sp.getChunkDeliveryMsgRetrievalPrice(), // arbitrary price for now
  			PerByte: true,
  			Payer:   protocols.Receiver,
  		},
  		reflect.TypeOf(RetrieveRequestMsg{}): {
  			Value:   sp.getRetrieveRequestMsgPrice(), // arbitrary price for now
  			PerByte: false,
  			Payer:   protocols.Sender,
  		},
  	}
  	r.prices = sp
  }
docs: // createPriceOracle sets up a matrix which can be queried to get
  // the price for a message via the Price method