697.—Any exception, exemption, proviso, excuse, or qualification, in relation to any offence under this Act, whether it does or does not accompany in the same section the description of the offence, may be proved by the defendant, but need not be specified or negatived in any information or complaint, and, if so specified or negatived, no proof in relation to the matter so specified or negatived shall be required on the part of the informant or complainant.