code: public boolean removeOrderbookCallback(final BitfinexOrderBookSymbol symbol,
  			final BiConsumer<BitfinexOrderBookSymbol, BitfinexOrderBookEntry> callback) throws BitfinexClientException {
  		return channelCallbacks.removeCallback(symbol, callback);
  	}
docs: Remove the a trading orderbook callback
  @param symbol
  @param callback
  @return true/false
  @throws BitfinexClientException