Additional property cannot be generated correctly in Monitor module/model MultiMetricCriteria

[JoyerJin]

README.md in PR Azure/azure-powershell#26931

Definition:
"MultiMetricCriteria": {
"type": "object",
"additionalProperties": {
"type": "object"
},
...
}
Swagger: https://github.com/Azure/azure-rest-api-specs/blob/92cf370fd73318f3cf92c36403274ba695873857/specification/monitor/resource-manager/Microsoft.Insights/stable/2018-03-01/metricAlert_API.json#L898

directive:

• from: metricAlert_API.json
  where: $.definitions.MultiMetricCriteria
  transform: $['additionalProperties'] = true

Expected and Actual:

[dolauli]

This issue happens when an object both contains properties and additional properties.