code: def lib_dir(self):
          
          if not self._lib_dir:
              rpm_lib_dir = None
              cmd = '{0} -ql rpm-libs'.format(self.rpm_path)
              out = Cmd.sh_e_out(cmd)
              lines = out.split('\n')
              for line in lines:
                  if 'librpm.so' in line:
                      rpm_lib_dir = os.path.dirname(line)
                      break
              self._lib_dir = rpm_lib_dir
          return self._lib_dir
docs: Return standard library directory path used by RPM libs.
  
          TODO: Support non-system RPM.