3. Property prediction: the input x is a single molecule, and the output y is the predicted property, which can be (1) a binary classification (True/False), for tasks such as blood-brain barrier penetration (BBBP), toxicity to humans (ClinTox), HIV replication inhibition (HIV), and drug side effects (SIDER), or (2) a continuous numeric value, for properties such as water solubility (ESOL) or the octanol/water distribution coefficient (LIPO).