One of the main issues with graph generative models is that the action space can grow dangerously large, making it very challenging to train models that generate big molecules [42]. This is not the case of SMILES generative models, as they only have to choose every epoch among a limited number of options (i.e., the vocabulary). On the other hand, SMILES models traverse the graph in a very specific way, they do not allow as many options as graph models.