code: function onChildRemoved(dbRef, callback, cancelCallbackOrContext, context) {
  		return dbRef.on('child_removed', callback, cancelCallbackOrContext, context);
  	}
docs: Wrapper around Firebase on child_removed listener.
  @param {*} dbRef Database reference to listen at.
  @param {*} callback A callback that fires when the specified event occurs. The callback will be passed a DataSnapshot. For ordering purposes, "child_added", "child_changed", and "child_moved" will also be passed a string containing the key of the previous child, by sort order, or null if it is the first child.
  @param {*} cancelCallbackOrContext An optional callback that will be notified if your event subscription is ever canceled because your client does not have permission to read this data (or it had permission but has now lost it). This callback will be passed an Error object indicating why the failure occurred.
  @param {*} context If provided, this object will be used as this when calling your callback(s).