title: How to use start_at() & end_at() in Firebase query with Python?
body: <p>My Firebase realtime database schema:</p>
  <p><img src="https://i.stack.imgur.com/JWMkM.png" alt="schema" /></p>
  <p>Let's suppose above Firebase database schema.
  I want to get data with <code>order_by_key()</code> which after first 5 and before first 10 not more. Range should be 5-10. Like in the image.</p>
  <p>My key is always starting with <code>-</code>.</p>
  <p>I'm trying this but failed. It returns 0. How can I do this?</p>
  <pre><code>snapshot = ref.child('tracks').order_by_key().start_at('-\5').end_at(u'-\10').get()
  </code></pre>