ChemPer creates SMIRKS patterns based on molecules in a training set, meaning it depends on cheminformatics toolkits to access properties of atoms and bonds in those molecules. Specifically, OpenEye toolkits or the RDKit [1] packages are used to access information about the atoms and bonds used when creating SMIRKS patterns. The mol_toolkit module includes three classes, Mol, Atom, and Bond which wrap around the corresponding molecule, atom, and bond objects in a dependent toolkit. These wrappers allow a user access to the rest of ChemPer tools without specifying which toolkit they are using. This setup allows for future support of other cheminformatics toolkits assuming the functions detailed below can be created.