def on_row_completed(self, callable):
self._on_row_completed.append(callable)<EOL>
Add an observer for completed rows.

        :param callable: a callable that is called with the row index as first
          argument

        When :meth:`row_completed` was called, this :paramref:`callable` is
        called with the row index as first argument. Call this method several
        times to register more observers.