, where each row of p f ragment sums to 1. We can then sample the discrete categorical latent z add ∈ {1, ..., k} d from p f ragment . The fragment to add is then obtained by deocoding z add through the learned frozen fragment decoder. We then assemble the decoded fragment with the current molecular graph by attaching the fragment to the predicted attachment point v add . Note that the attachment point over the fragment is indicated through the generated SELFIES string.