Sublassing NumericColumn prevents subtotals from working

[rsyring]

class RevCol(NumericColumn):
    def __init__(self, *args, **kwargs):
        super().__init__(*args, places=0, curr='$', **kwargs)


class DashboardProjects(GridBase):
    subtotals = 'grand'

    NumericColumn('Total', ents.Project.rev_total, group=Revenue, has_subtotal='sum')
    RevCol('Invoiced', ents.Project.rev_invoiced, group=Revenue, has_subtotal='sum')

Something like the above does not work as expected. has_subtotal does not make it to the "new" column instance when its created in Column.new_instance().