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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def _evaluate_group_dataframe(self, gdf):
 """ Evaluate a single group dataframe Parameters gdf : pandas.DataFrame Input group dataframe Returns ------- out : pandas.DataFrame Result data """

        gdf._is_copy = None
        result_index = gdf.index if self.keep_index else []
        data = pd.DataFrame(index=result_index)
        for expr in self.expressions:
            value = expr.evaluate(gdf, self.env)
            if isinstance(value, pd.DataFrame):
                data = value
                break
            else:
                _create_column(data, expr.column, value)
        data = _add_group_columns(data, gdf)
        return data