The creation of a focused virtual chemical library with a CLM generally includes three basic steps: (i) model pretraining with a large set of molecules to learn the SMILES grammar and the feature distribution of the pretraining data, (ii) transfer learning with a smaller set of molecules (fine-tuning set) to bias the molecule generation by the CLM toward the chemical space of interest, and (iii) sampling of new molecules from the data distributions modeled in steps i) and ii) . There are alternative approaches for CLM development, e.g., model fine-tuning (step ii) by reinforcement learning .