code: def archive_path(self, real_path):
          
          if (not self.path_prefix):
              return(real_path)
          else:
              return(os.path.relpath(real_path, self.path_prefix))
docs: Return the archive path for file with real_path.
  
          Mapping is based on removal of self.path_prefix which is determined
          by self.check_files().