如何指示亚马逊网络服务CloudFormation模板在特定区域创建资源？

"Metadata" : {
  "AWS::CloudFormation::Interface" : {
    "ParameterGroups" : [
      {
        "Label" : {
          "default" : "AWS Region Configuration"
        },
        "Parameters" : ["AWSRegion"]
      }
    ],
    "ParameterLabels" : {
      "AWSRegion" : {
        "default" : "AWS Region"
      }
    }
  }
}

"Parameters" : {
  "AWSRegion" : {
    "Description" : "AWS region where the resources will be created",
    "Type" : "AWS::EC2::AvailabilityZone::RegionName",
    "Default" : "us-east-1"
  }
}

"Resources" : {
  "MyEC2Instance" : {
    "Type" : "AWS::EC2::Instance",
    "Properties" : {
      "ImageId" : "ami-12345678",
      "InstanceType" : "t2.micro",
      "AvailabilityZone" : { "Fn::Join" : [ "", [ { "Ref" : "AWSRegion" }, "a" ] ] }
    }
  }
}