code: def gzip_files(self):
          
          ret_list = []
          for key, val in self.file_dict.items():
              # For temp files we only want files that were marked for removal
              if val & FileFlags.gz_mask:
                  ret_list.append(key)
          return ret_list
docs: Return a list of the files compressed by this link.
  
          This returns all files that were explicitly marked for compression.