Perform ``self.recode`` and add resulting column(s) to ``df`` and return ``df``.

def update_dataframe(self, df, table, validate=False):
        """Perform ``self.recode`` and add resulting column(s) to ``df`` and return ``df``."""
        df = df.copy()
        recoded_columns = self.recode(table=table, validate=validate)
        return pd.concat([df, recoded_columns], axis=1)