A LOF value close to 1 indicates that a point is located in a similarly dense region as its neighbours. A LOF value less than 1 represents an inlier, meaning that the point is situated in a denser region, while a value greater than 1 indicates an outlier. Since there is no definitive rule for selecting an LOF threshold to identify outliers, in this study, we chose the threshold as an LOF value which is larger than 80 % of LOF values for the given training set. This approach ensures that the threshold value varies with the PES exploration during the AL iterations. More details of the distance selector are provided in SI § 3.2.