if (key >= SEMI.N()) bpl_utils::throw_index_out_of_range();
if (key >= SEMI.N()) bpl_utils::raise_index_error();
  SymEquivIndices_getitem(const SymEquivIndices& SEMI,                                std::size_t key) {    if (key >= SEMI.N()) bpl_utils::throw_index_out_of_range();    return SEMI[key];  }