gistfile1.py

        # if we get both or neither, no good
        if not (bool(timeAssignment) ^ bool(dropTake)):
            raise DropError('drop() takes either a ' + self.family.RecurringTimeAssignment.__name__ + ' or ' + self.family.DropTake.__name__ + ' as an argument but not both nor neither')
        if timeAssignment and not type(timeAssignment) == self.family.RecurringTimeAssignment:
            raise TypeError('timeAssignment must be a ' + self.family.RecurringTimeAssignment.__name__)
        if dropTake and not type(dropTake) == self.family.DropTake:
            raise TypeError('dropTake must be a '+ self.family.DropTake.__name__)