code: def next(self):
      
      options = {}
      if self._buffer_size:
        options["read_buffer_size"] = self._buffer_size
      if self._account_id:
        options["_account_id"] = self._account_id
      while True:
        filename = self._next_file()
        if filename is None:
          raise StopIteration()
        try:
          start_time = time.time()
          handle = cloudstorage.open(filename, **options)
  
          ctx = context.get()
          if ctx:
            operation.counters.Increment(
                COUNTER_IO_READ_MSEC, int((time.time() - start_time) * 1000))(ctx)
  
          return handle
        except cloudstorage.NotFoundError:
          # Fail the job if we're strict on missing input.
          if getattr(self, "_fail_on_missing_input", False):
            raise errors.FailJobError(
                "File missing in GCS, aborting: %s" % filename)
          # Move on otherwise.
          logging.warning("File %s may have been removed. Skipping file.",
                          filename)
docs: Returns the next input from this input reader, a block of bytes.
  
      Non existent files will be logged and skipped. The file might have been
      removed after input splitting.
  
      Returns:
        The next input from this input reader in the form of a cloudstorage
        ReadBuffer that supports a File-like interface (read, readline, seek,
        tell, and close). An error may be raised if the file can not be opened.
  
      Raises:
        StopIteration: The list of files has been exhausted.