code: def build_default_simulation(self, tax_benefit_system, count = 1):
          
  
          simulation = Simulation(tax_benefit_system, tax_benefit_system.instantiate_entities())
          for population in simulation.populations.values():
              population.count = count
              population.ids = np.array(range(count))
              if not population.entity.is_person:
                  population.members_entity_id = population.ids  # Each person is its own group entity
          return simulation
docs: Build a simulation where:
                  - There are ``count`` persons
                  - There are ``count`` instances of each group entity, containing one person
                  - Every person has, in each entity, the first role