code: def append(self, data):
      
      data_length = len(data)
      if self._size + data_length > self._flush_size:
        self.flush()
  
      if not self._exclusive and data_length > _FILE_POOL_MAX_SIZE:
        raise errors.Error(
            "Too big input %s (%s)."  % (data_length, _FILE_POOL_MAX_SIZE))
      else:
        self._buffer.append(data)
        self._size += data_length
  
      if self._size > self._flush_size:
        self.flush()
docs: Append data to a file.