CloudFormation Template传递TargetDescription列表的参数类型

Question

我有一个正在使用的CFT模板，我们使用一个子网来克隆其行为，但是要使用目标组Targets属性。

Subnets: 
  Description: description here
  Type: List<AWS::EC2::Subnet::Id>

lbTargets:
  Description: some stuff here
  Type: List<AWS::EC2::Instance::Id>


#later we reference subnets like this
Subnets: !Ref Subnets


#This is the part that isnt working and it is somewhere int the typing since 
!Refs Subnets returns a list of strings and that would make it the 
valid type that Subnets is expecting, where Targets expects a list of 
TargetDescription

Targets: !Ref lbTargets

有人知道如何将lbTargets强制为一种TargetDescription吗？