def METHOD_NAME(self):
    """Digest info in the statepoint and return as a string."""
    # Read the statepoint file.
    sp = openmc.StatePoint(self._sp_name)
    # Extract the tally data as a Pandas DataFrame.
    tally_dfs = [t.get_pandas_dataframe() for t in sp.tallies.values()]
    df = pd.concat(tally_dfs, ignore_index=True)
    # Extract the relevant data as a CSV string.
    cols = ('mean', 'std. dev.')
    return df.to_csv(None, columns=cols, index=False, float_format='%.7e')
    return outstr