iterator compile_unit_begin() const { return CUs.begin(); }
iterator compile_unit_end() const { return CUs.end(); }
iterator subprogram_begin() const { return SPs.begin(); }
iterator compile_unit_begin() const { return CUs.begin(); }
iterator compile_unit_end() const { return CUs.end(); }
iterator subprogram_begin() const { return SPs.begin(); }