allow enums as input args
allow enums as input args

leiyangyou/libvips,lovell/libvips,jcupitt/libvips,lovell/libvips,mcanthony/libvips,lovell/libvips,wishabi/libvips,wishabi/libvips,mcanthony/libvips,jcupitt/libvips,lovell/libvips,wishabi/libvips,mcanthony/libvips,leiyangyou/libvips,leiyangyou/libvips,jcupitt/libvips,leiyangyou/libvips,mcanthony/libvips,jcupitt/libvips,wishabi/libvips