Making sense of a package with almost no files included

$ uname -a Linux laptop 4.19.0-2-amd64 #1 SMP Debian 4.19.16-1 (2019-01-17) x86_64 GNU/Linux I need to use cv::face::createLBPHFaceRecognizer(), which is not a part of the core OpenCV but rather a contributed module. $ dpkg -l libopencv-contrib-dev ii libopencv-contrib-dev:amd64 3.2.0+dfsg-6 amd64 development files for libopencv-contrib3.2 everything fine ... no: src/cmd.cpp:150: error: ‘cv::face’ has not been declared const auto model = cv::face::createLBPHFaceRecognizer(); ^~~~ OK. Let's then include the needed headers manually: $ dpkg -S libopencv-contrib-dev libopencv-contrib-dev:amd64: /usr/share/doc/libopencv-contrib-dev libopencv-contrib-dev:amd64: /usr/share/doc/libopencv-contrib-dev/changelog.Debian.gz libopencv-contrib-dev:amd64: /usr/share/doc/libopencv-contrib-dev/copyright libopencv-contrib-dev:amd64: /usr/share/doc/libopencv-contrib-dev/README.Debian Nothing! Is this a packager's mistake (this is Debian **testing** after all)? An OpenCV peculiarity? A minor oversight on my side? I would like to continue using the package manager, instead of compiling the whole thing myself.