A similar strategy was explored for molecular property prediction. o Masking of functional groups, whereby atoms belonging to pre-defined functional groups are masked. This is based on the hypothesis that masking functional groups might improve the learning of the 'chemical semantics' compared to random masking. A pre-defined list of 'chemically relevant' functional groups was used (Supp. Figure ). In both cases, the probability of atoms getting masked is controlled by a user-defined probability (p).