if (key >= WP.M()) bpl_utils::throw_index_out_of_range();
if (key >= WP.M()) bpl_utils::raise_index_error();
  RTMx WyckoffPosition_getitem(const WyckoffPosition& WP,                               std::size_t key)  {    WP.CheckExpanded();    if (key >= WP.M()) bpl_utils::throw_index_out_of_range();    return WP(key);  }