使用ansible循环在列表字典上迭代

我有下面的测试剧本来循环列表字典

- hosts: localhost

  connection: local

  vars:

    machine_roles:

      masters: ["master1","master2"]
      workers: ["worker1","worker2"]

  tasks:

    - name: toto
      debug:
       msg: "{{ item.0.role}} --- {{ item.1 }}"

      loop:
        - "{{ machine_roles | dict2items(key_name='role', value_name='machine') | subelements('machine') }}"

我希望得到以下输出：

masters --- master1
masters --- master2
workers --- worker1
workers --- worker2

基于我对文档和类似帖子的理解，我希望我的剧本能完成这项工作。但是，在运行它时，我得到以下错误：

fatal: [localhost]: FAILED! => {"msg": "The task includes an option with an undefined variable. The error was: 'list object' has no attribute 'role'\n\nThe error appears to be in '/root/git/visa-jupyter/jupyterhub-kubespawner/test.yml': line 14, column 7, but may\nbe elsewhere in the file depending on the exact syntax problem.\n\nThe offending line appears to be:\n\n\n    - name: toto\n      ^ here\n"}

令人惊讶的是，在调试

{{machine|roles | dict2items（key_name='role'，value_name='machine'）| subelements（'machine'）}

的结果时，我得到了：

    [
        [
            {
                "machine": [
                    "master1", 
                    "master2"
                ], 
                "role": "masters"
            }, 
            "master1"
        ], 
        [
            {
                "machine": [
                    "master1", 
                    "master2"
                ], 
                "role": "masters"
            }, 
            "master2"
        ], 
        [
            {
                "machine": [
                    "worker1", 
                    "worker2"
                ], 
                "role": "workers"
            }, 
            "worker1"
        ], 
        [
            {
                "machine": [
                    "worker1", 
                    "worker2"
                ], 
                "role": "workers"
            }, 
            "worker2"
        ]
    ]

在我看来，当组合

dict2items

和

子元素时，这就是文档中解释的预期结果

为什么在此数据结构上应用
loop
命令会失败，或者至少不会产生我所期望的结果

[编辑和回答]
我终于找到了错误。我通过以下操作引入了另一个循环关卡，让自己大吃一惊：

loop:
  - "{{ machine_roles | dict2items(key_name='role', value_name='machine') | subelements('machine') }}"

正确的语法是（就我而言）：

这一定是一些奇怪的格式/缩进问题。您的代码运行良好

"msg": "masters --- master1"
"msg": "masters --- master2"
"msg": "workers --- worker1"
"msg": "workers --- worker2"

FWIW。这是到测试的链接。
我终于找到了我的错误。Cf我的编辑信息。与你的版本相比，我找到了方向。谢谢
"msg": "masters --- master1"
"msg": "masters --- master2"
"msg": "workers --- worker1"
"msg": "workers --- worker2"