Firebase Analytics begin_checkout Items

Recently, I've implemented Firebase Analytics AnalyticsEventBeginCheckout event. But it seems AnalyticsParameterItems not be sent to Firebase.

My code :

var jeggings: [String: Any] = [
      AnalyticsParameterItemID: "SKU_123",
      AnalyticsParameterItemName: "jeggings",
      AnalyticsParameterItemCategory: "pants",
      AnalyticsParameterItemVariant: "black",
      AnalyticsParameterItemBrand: "Google",
      AnalyticsParameterPrice: 9.99,
    ]

    // A pair of boots
var boots: [String: Any] = [
      AnalyticsParameterItemID: "SKU_456",
      AnalyticsParameterItemName: "boots",
      AnalyticsParameterItemCategory: "shoes",
      AnalyticsParameterItemVariant: "brown",
      AnalyticsParameterItemBrand: "Google",
      AnalyticsParameterPrice: 24.99,
    ]

var checkoutParams: [String: Any] = [
      AnalyticsParameterCurrency: "USD",
      AnalyticsParameterValue: 14.98,
      AnalyticsParameterCoupon: "SUMMER_FUN"
    ];

checkoutParams[AnalyticsParameterItems] = [jeggings, boots]

    // Log checkout event
Analytics.logEvent(AnalyticsEventBeginCheckout, parameters: checkoutParams)

This code is the tutorial code from Firebase.

It seems AnalyticsParameterItems not been send, but if I send item_id and item_name, these 2 fields appear on my event datas

Any solution ?