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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def next(self):
 """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. """

    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)