title: Query nested JSON data with Pymongo
body: <p>I have MongoDB documents that looks like this (unimportant data removed for clarity):</p>
  
  <pre><code>{
    "posts": [
      {
        "id": 1234,
        "comments": "I want this data!"
      },
      {
        "id": 4444,
        "comments" "foo"
      }
    ]
  }
  </code></pre>
  
  <p>With only the knowledge that it's in the object with id=1234, how can I use Pymongo (Python 3) to return the "comments" value, ie "I want this data!"?</p>
  
  <p>Thanks</p>