The data goes into `pyne::endf::library.struct_list`. The workflow idea is to use `read_endf` on one or more files then check what you got with `get_library_contents()` then copy a specific dataset from `pyne::endf::library.struct_list` into the appropriate struct container using `pyne::endf::load_dataset_to_API(int mat, int mf, int mt)` which then gives you easy cython access to that struct via `endfcpp.mt_xxx`.