nd4j-backends/nd4j-api-parent/nd4j-api/src/main/java/org/nd4j/autodiff/samediff/SameDiff.java
public INDArray execBackwardAndEndResult() {
        List<DifferentialFunction> backwards = execBackwards().getRight();
        DifferentialFunction df = backwards.get(backwards.size() - 1);
        if (df instanceof Op) {
            return ((Op) df).z();
        } else if (df instanceof DynamicCustomOp) {
            return ((DynamicCustomOp) df).getOutputArgument(0);
        } else {
            return null;
        }
    }
public INDArray execBackwardAndEndResult() {
        List<DifferentialFunction> backwards = execBackwards().getRight();
        DifferentialFunction df = backwards.get(backwards.size() - 1);
        if (df instanceof Op) {
            return ((Op) df).z();
        } else if (df instanceof DynamicCustomOp) {
            return ((DynamicCustomOp) df).getOutputArgument(0);
        } else {
            return null;
        }
    }
Exec a backwards operation
and return the end result

@return