docs: public Map<String, OptionalFailure<Accumulator<?, ?>>> aggregateUserAccumulators() {
  
  		Map<String, OptionalFailure<Accumulator<?, ?>>> userAccumulators = new HashMap<>();
  
  		for (ExecutionVertex vertex : getAllExecutionVertices()) {
  			Map<String, Accumulator<?, ?>> next = vertex.getCurrentExecutionAttempt().getUserAccumulators();
  			if (next != null) {
  				AccumulatorHelper.mergeInto(userAccumulators, next);
  			}
  		}
  
  		return userAccumulators;
  	}