title: Firebase: initialize a tree made of collections
body: <p>I built a tree consisting of a set of collections. Each collection is in turn made of other sub-collections and so on.</p>
  
  <p>Every collection has the same field (which is the one I want to update).</p>
  
  <p>Is there a way to update every level of the tree with the same value (in order to initialize it)?</p>
  
  <p>Some images of the tree's structure:<a href="https://i.stack.imgur.com/7PLlR.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/7PLlR.png" alt="enter image description here"></a></p>