code: public void registerExecutedTradeCallback(final BitfinexExecutedTradeSymbol orderbookConfiguration,
  			final BiConsumer<BitfinexExecutedTradeSymbol, BitfinexExecutedTrade> callback) throws BitfinexClientException {
  
  		tradesCallbacks.registerCallback(orderbookConfiguration, callback);
  	}
docs: Register a new executed trade callback
  @param symbol
  @param callback
  @throws BitfinexClientException