from trytond.pool import Pool, PoolMeta
from trytond.model import ModelView, fields
from trytond.exceptions import UserError
from trytond.pyson  import Eval


class InvoiceLine(metaclass=PoolMeta):
    __name__ = 'account.invoice.line'

    @classmethod
    def __setup__(cls):
        super(InvoiceLine, cls).__setup__()

        cls.product.states['required'] = (Eval('type') == 'line')
        cls.unit_price.domain = []