title: How to get array from nlohmann json
body: <p>I tried to search how to get array from json using JSON for Modern C++, but I couldn't find answer. </p>
  
  <p>I have json like this:</p>
  
  <pre><code>{
    "Command": "cmd",
    "Data":{"time": 200, "type":1},
    ...
  }
  </code></pre>
  
  <p>And I want to ask how to get object with key "Data", how to store it and how to access it's elements (count of elements and keys in data can change depending on command).</p>
  
  <p>Thanks for help</p>