def __init__(self, sql):
        super(HistoryTable, self).__init__(sql)
        # Check that first column is the effective timestamp
        # And the second column is the expiration timestamp
        if self.column(HIST_EFFECTIVE_COLUMN) is None or\
                self.column(HIST_EXPIRATION_COLUMN) is None:
            raise ValueError('History table must have effective and expiration'
                             ' timestamps')
Returns the field name and direction for an order specification. For
dataset/ETHPy150Open coursera/dataduct/dataduct/database/history_table.py/HistoryTable.__init__--crossover with--dataset/ETHPy150Open django/django/django/db/models/sql/query.py/get_order_dir