def decrement(self, column, amount=1, extras=None):
        wrapped = self._grammar.wrap(column)

        if extras is None:
            extras = {}

        columns = {
            column: self.raw('%s - %s' % (wrapped, amount))
        }
        columns.update(extras)

        return self.update(**columns)
Decrement a column's value by a given amount
dataset/ETHPy150Open sdispater/orator/orator/query/builder.py/QueryBuilder.decrement