docs: public Gradient backpropGradient(INDArray... epsilons) {
          if (epsilons == null || epsilons.length != numOutputArrays)
              throw new IllegalArgumentException(
                      "Invalid input: must have epsilons length equal to number of output arrays");
  
  
          try {
              calcBackpropGradients(true, configuration.getBackpropType() == BackpropType.TruncatedBPTT, epsilons);
              return gradient;
          } catch (OutOfMemoryError e){
              CrashReportingUtil.writeMemoryCrashDump(this, e);
              throw e;
          }
      }