where nu * ∥zs means the concatenation of the embedding of u * and graph-level embedding zs, U t ∈ R 1×d MLP and W t ∈ R d MLP ×2dc are the trainable parameters. If f t u * > 0.5, our model predicts the synthon to be a complete molecule, otherwise, we add a motif to the synthon, leading to the following motif prediction task.