code: def _lock(self, break_existing=False):
          
          # write("_lock")
          data = {"lock_time": time.time(), "lock_holder": None}
  
          try:
              assert self.cur_dir == self.root_dir
              self.write_text(DirMetadata.LOCK_FILE_NAME, json.dumps(data))
              self.lock_data = data
              self.lock_write_time = time.time()
          except Exception as e:
              errmsg = "{}".format(e)
              write_error("Could not write lock file: {}".format(errmsg))
              if errmsg.startswith("550") and self.ftp.passiveserver:
                  try:
                      self.ftp.makepasv()
                  except Exception:
                      write_error(
                          "The server probably requires FTP Active mode. "
                          "Try passing the --ftp-active option."
                      )
  
              # Set to False, so we don't try to remove later
              self.lock_data = False
docs: Write a special file to the target root folder.