docs: function countChildScopes() {
      // jshint validthis: true
      var count = 0; // exclude the current scope
      var pendingChildHeads = [this.$$childHead];
      var currentScope;
  
      while (pendingChildHeads.length) {
        currentScope = pendingChildHeads.shift();
  
        while (currentScope) {
          count += 1;
          pendingChildHeads.push(currentScope.$$childHead);
          currentScope = currentScope.$$nextSibling;
        }
      }
  
      return count;
    }