title: only get specific childs in Firebase
body: <pre><code>{
    "chat" : {
      "-JZvOzp0L1ccuBt2TVN7" : {
        "author" : "JavaUser21221",
        "message" : "hello "
      },
      "-JZvPneW5et0_EVRvL5g" : {
        "author" : "JavaUser21221",
        "message" : "hai"
      }
  }
  </code></pre>
  
  <p>Is it possible to only get the messages?</p>