docs: def absolutize(self, region_id, relative_address):
          """
          Convert a relative address in some memory region to an absolute address.
  
          :param region_id:           The memory region ID
          :param relative_address:    The relative memory offset in that memory region
          :return:                    An absolute address if converted, or an exception is raised when region id does not
                                      exist.
          """
  
          if region_id == 'global':
              # The global region always bases 0
              return relative_address
  
          if region_id not in self._region_id_to_address:
              raise SimRegionMapError('Non-existent region ID "%s"' % region_id)
  
          base_address = self._region_id_to_address[region_id].base_address
          return base_address + relative_address