private double[] getDeltaValues(double[][] weights, double[] neuronOutputs) {
        assert weights[0].length == neuronOutputs.length :
            "Number of output neurons in weights array not equal to number of outputs.";

        double[] delta = new double[weights.length];

        for (int input = 0; input < delta.length; input++) {
            
            double sum = 0;
            for (int output = 0; output < neuronOutputs.length; output++) {
                
                sum += weights[input][output] * neuronOutputs[output];
            }

            delta[input] = sum;
        }

        return delta;
    }