5. Article 30 of the TRIPS Agreement allows Member countries to provide limited exceptions to the exclusive rights granted by the patent provided these exceptions do not "unreasonably conflict with a normal exploitation of the patent and do not unreasonably prejudice the legitimate interests of the patent owner". Article 4 of the South African patent law provides for an exception to a patent owner’s rights for "public purposes". Please explain how this provision is interpreted and applied in practice, and how it complies with Article 30.