Returns a column as a Series.

        Parameters
        ----------
        column_name : str

        Returns
        -------
        column : pandas.Series

def get_column(self, column_name):
        """
        Returns a column as a Series.

        Parameters
        ----------
        column_name : str

        Returns
        -------
        column : pandas.Series

        """
        with log_start_finish(
                'getting single column {!r} from table {!r}'.format(
                    column_name, self.name),
                logger):
            extra_cols = _columns_for_table(self.name)
            if column_name in extra_cols:
                with log_start_finish(
                        'computing column {!r} for table {!r}'.format(
                            column_name, self.name),
                        logger):
                    column = extra_cols[column_name]()
            else:
                column = self.local[column_name]
            if self.copy_col:
                return column.copy()
            else:
                return column