title: Iterate over all machine inner documents
body: <p>I got this JSON and I want to iterate over all inner fields inside machine: <code>machine.id</code> (inner machine objects, one by one and get the id)</p>
  <pre><code>{
      &quot;_id&quot; : ObjectId(&quot;60b72eb607d158d886626648&quot;),
      &quot;accountId&quot; : &quot;10304&quot;,
      &quot;dayKey&quot; : 20210602,
      &quot;twin&quot; : &quot;c9750367-36fe-4e1f-a9bb-54f44c1cd8d8&quot;,
      &quot;ttl&quot; : ISODate(&quot;2021-06-02T07:09:37.515Z&quot;),
      &quot;machines&quot; : {
          &quot;dff2a2c3-6765-425a-8cb8-26b3f9c6214d-machine-54652&quot; : {
             
              &quot;ioSize&quot; : [ 
                  14.7014119238827, 
                  14.1548860858939, 
                  14.5505302898045, 
                  15.554507463338, 
                  14.4255739350559, 
                  14.5063722067039, 
                  15.459819090433, 
                  14.3030780813547, 
                  14.1884056389665, 
                  14.4948280377095, 
                  13.3577492143855, a
                  14.7608731232542, 
                  15.9873265101257, 
                  13.4887886260475, 
                  15.7738139402933, 
                  15.9362888442737, 
                  14.7705187238128
              ],
              &quot;id&quot; : &quot;dff2a2c3-6765-425a-8cb8-26b3f9c6214d.machine-54652&quot;
          },
          &quot;dff2a2c3-6765-425a-8cb8-26b3f9c6214d-machine-35562&quot; : {
              
              &quot;ioSize&quot; : [ 
                  37.7397106319832, 
                  38.9988270338687, 
                  38.5746933921089, 
                  38.0871104661313, 
                  39.2368627793296, 
                  38.5768210981145, 
                  40.0075015275838, 
                  38.4587879713687, 
                  38.7158966916899, 
                  38.8449393331006, 
                  38.9401787273045, 
                  38.6076837465084, 
                  39.5514468400838, 
                  46.7157111993715, 
                  48.3111469972067, 
                  38.5859375, 
                  38.9902398306564
              ],
              &quot;id&quot; : &quot;dff2a2c3-6765-425a-8cb8-26b3f9c6214d.machine-35562&quot;
        
          }
      }
  }
  </code></pre>