title: Firebase remove node based on child value
body: <p>I want to delete the entire node by query like delete * WHERE user_id = "-KTruPWrYO9WFj-TF8Ft" How can I achieve this on firebase?</p>
  
  <pre><code>-KVpQFXnzQkzzrowHxGk
    answer: "1"
    question_number: 2
    user_id: "-KTruPWrYO9WFj-TF8Ft"
  -KVpQFXODhsAMJYFNjy7
    answer: "4"
    question_number: 25
    user_id: "-KTruPWrYO9WFj-TF8Ft"
  </code></pre>