ARM模板-如何引用copyIndex()部署输出？

{
  "$schema": "https://schema.management.azure.com/schemas/2019-04-01/deploymentTemplate.json#",
  "contentVersion": "1.0.0.0",
  "parameters": {},
  "variables": {},
  "resources": [],
  "outputs": {
    "output1": {
      "type": "string",
      "value": "[copyIndex()]"
    }
  },
  "copy": {
    "name": "copyLoop",
    "count": 3,
    "mode": "Serial",
    "actions": [
      {
        "type": "Microsoft.Resources/deployments",
        "name": "[concat('deployment', copyIndex())]",
        "apiVersion": "2019-10-01",
        "properties": {
          "mode": "Incremental",
          "template": {
            "$schema": "https://schema.management.azure.com/schemas/2019-04-01/deploymentTemplate.json#",
            "contentVersion": "1.0.0.0",
            "resources": [],
            "outputs": {
              "output2": {
                "type": "string",
                "value": "[copyIndex()]"
              }
            }
          }
        }
      }
    ]
  }
}