code: public boolean removeCallback(final S symbol, final BiConsumer<S, T> callback) throws BitfinexClientException {
  		
  		final List<BiConsumer<S, T>> callbackList = callbacks.get(symbol);
  
  		if(callbackList == null) {
  			throw new BitfinexClientException("Unknown ticker string: " + symbol);
  		}			
  		
  		return callbackList.remove(callback);	
  	}
docs: Remove the a callback
  @param symbol
  @param callback
  @return
  @throws BitfinexClientException