docs: @Override
  	public void set(final Iterator<Tuple2<KEY, VALUE>> iterator) {
  		this.iterator = iterator;
  		if (this.hasNext()) {
  			final Tuple2<KEY, VALUE> tuple = iterator.next();
  			this.curKey = keySerializer.copy(tuple.f0);
  			this.firstValue = tuple.f1;
  			this.atFirst = true;
  		} else {
  			this.atFirst = false;
  		}
  	}