docs: def unwrap(self, value, session=None):
          ''' Validate and then unwrap ``value`` for object creation.
  
              :param value: list returned from the database.
          '''
          self.validate_unwrap(value)
          ret = []
          for field, value in izip(self.types, value):
              ret.append(field.unwrap(value, session=session))
          return tuple(ret)