unsigned OEGetAromaticRingCount(const OEChem::OEMolBase &mol)
Returns the number of aromatic rings in a molecule as defined in [Ritchie-2009]. The article describes the method as the following:
The terminology 'number of aromatic rings' (or aromatic ring count) is used generically and encompasses both benzenoid aromatic rings and heteroaromatics (including, e.g. pyridine and imidazole). ... Each ring in a fused system is counted individually; thus, indole and naphthalene are each defined as having two aromatic rings.