code: def value_nth_person(self, n, array, default = 0):
          self.members.check_array_compatible_with_entity(array)
          positions = self.members_position
          nb_persons_per_entity = self.nb_persons()
          members_map = self.ordered_members_map
          result = self.filled_array(default, dtype = array.dtype)
          result[nb_persons_per_entity > n] = array[members_map][positions[members_map] == n]
          return result