code: def handle_units(changeset):
      
      units, records = {}, {}
      for service_name, service in sorted(changeset.bundle['services'].items()):
          for i in range(service.get('num_units', 0)):
              record_id = 'addUnit-{}'.format(changeset.next_action())
              unit_name = '{}/{}'.format(service_name, i)
              records[record_id] = {
                  'id': record_id,
                  'method': 'addUnit',
                  'args': [
                      '${}'.format(changeset.services_added[service_name]),
                      None,
                  ],
                  'requires': [changeset.services_added[service_name]],
              }
              units[unit_name] = {
                  'record': record_id,
                  'service': service_name,
                  'unit': i,
              }
      _handle_units_placement(changeset, units, records)
docs: Populate the change set with addUnit changes.