In this file, you can see that supported file formats for meshes are registered when the OpenGeode_IO_mesh library is loaded. However, the I/O code is not directly called in the executable (see tests for examples). As a consequence, the OpenGeode_IO_mesh library is not loaded. This is called lazy loading of dependencies. By calling the function detail::initialize_mesh_io(), the library is loaded, the file formats are registered, and you can use our supported file formats.