Convert this SFrame to pandas.DataFrame.

        This operation will construct a pandas.DataFrame in memory. Care must
        be taken when size of the returned object is big.

        Returns
        -------
        out : pandas.DataFrame
            The dataframe which contains all rows of SFrame

def to_dataframe(self):
        """
        Convert this SFrame to pandas.DataFrame.

        This operation will construct a pandas.DataFrame in memory. Care must
        be taken when size of the returned object is big.

        Returns
        -------
        out : pandas.DataFrame
            The dataframe which contains all rows of SFrame
        """
        assert HAS_PANDAS, 'pandas is not installed.'
        df = pandas.DataFrame()
        for i in range(self.num_columns()):
            column_name = self.column_names()[i]
            df[column_name] = list(self[column_name])
            if len(df[column_name]) == 0:
                df[column_name] = df[column_name].astype(self.column_types()[i])
        return df