Bar plots showing the median error made by the network trained on the multi-label dataset on each class contribution for three example instances. The coloured bars represent the network’s prediction, while the empty bars are the true labels. In panel a, we show the classification of a single-label PNe spectrum, whose coefficients are accurately predicted. In panel b, we show the results for a multi-label instance, with a prevalent contribution of DIG > 60%. In panel c, we show the results for another multi-label instance, with a prevalent contribution of H II region = 60%.