title: nlohmann parsing a json file without knowing keys
body: <p>I'm using nlohmann/json library to use json in cpp. I have a Json::Value object and I would like to go through my json data by exploring the keys without knowing them. I came across the <a href="https://open-source-parsers.github.io/jsoncpp-docs/doxygen/class_json_1_1_value.html" rel="nofollow noreferrer">documentation</a> but only found the <code>object["mySuperKey"]</code> method to explore the datas which means to know the existing keys.</p>
  
  <p>Can you please give me some  tips ? </p>
  
  <p>thanks.</p>