code: public static void mergeInto(Map<String, Accumulator<?, ?>> target, Map<String, Accumulator<?, ?>> toMerge) {
  		for (Map.Entry<String, Accumulator<?, ?>> otherEntry : toMerge.entrySet()) {
  			Accumulator<?, ?> ownAccumulator = target.get(otherEntry.getKey());
  			if (ownAccumulator == null) {
  				// Take over counter from chained task
  				target.put(otherEntry.getKey(), otherEntry.getValue());
  			} else {
  				// Both should have the same type
  				AccumulatorHelper.compareAccumulatorTypes(otherEntry.getKey(),
  						ownAccumulator.getClass(), otherEntry.getValue().getClass());
  				// Merge counter from chained task into counter from stub
  				mergeSingle(ownAccumulator, otherEntry.getValue());
  			}
  		}
  	}
docs: Merge two collections of accumulators. The second will be merged into the
  first.
  
  @param target
  The collection of accumulators that will be updated
  @param toMerge
  The collection of accumulators that will be merged into the
  other