i was created a module with the constrains for showing warning message. I was followed odoo documentation, the thing is that user cant book the same room at same date.But after my interating code the warning message shows, even i cant able to book the room on different dates.Is it possible to do by two variables passes?? Please give me a solution.

code for constrain is:-

def _check_date(self, cr, uid,ids, context=None):

record = self.search(cr, uid,[('room_id', '=', self.room_id.id),('start', '=', self.start)])

if record:

return False

return True

_constraints = [(_check_date, 'Room already booked',['room_id','start'])]