query {
  listEvent(Id:"Event-b72a8064-cff6-47af-98a2-a8e17c48e9eb") {
    items {
      ...on Event {
        __typename
        Id
      }
      ...on EventDuty {
        __typename
        EntityId
      }
      ...on EventTeam {
        __typename
        EntityId
      }
    }
  }
}

produces the below result

{
  "data": {
    "listEvent": {
      "items": [
        {
          "__typename": "EventTeam",
          "EntityId": "Team-2"
        },
        {
          "__typename": "EventTeam",
          "EntityId": "Team-1"
        },
        {
          "__typename": "Event",
          "Id": "Event-b72a8064-cff6-47af-98a2-a8e17c48e9eb"
        },
        {
          "__typename": "EventDuty",
          "EntityId": "Duty-5"
        },
        {
          "__typename": "EventDuty",
          "EntityId": "Duty-3"
        },
        {
          "__typename": "EventDuty",
          "EntityId": "Duty-2"
        },
        {
          "__typename": "EventDuty",
          "EntityId": "Duty-1"
        }
      ]
    }
  }
}