code: def get_service_state_list() -> List[ServiceState]:
      
      keys = DB.get_keys('states*')
      LOG.debug('Loading list of known services.')
      services = []
      for key in keys:
          values = key.split(':')
          if len(values) == 4:
              services.append(ServiceState(*values[1:4]))
      return services
docs: Return a list of ServiceState objects known to SDP.