def add_sector(booking_id, date, from_loc, to_loc, service):
res = None
b = Booking.get_by_id(booking_id)
if b:
res = Sector(date=date, from_loc=from_loc, to_loc=to_loc, service=service, booking=b)
res.put()
if date > b.last_date:
b.last_date = date
b.put()
_use(b.key())
return res.to_dict()
