<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def _to_df(self, query, conn, index_col=None, coerce_float=True, params=None, parse_dates=None, columns=None):
 """ Internal convert-to-DataFrame convenience wrapper. """

        return pd.io.sql.read_sql(str(query), conn, index_col=index_col,
                                  coerce_float=coerce_float, params=params,
                                  parse_dates=parse_dates, columns=columns)