code: public void activate(String clientID) {
          for (Subscription s : m_subscriptions) {
              if (s.clientId.equals(clientID)) {
                  s.setActive(true);
              }
          }
  
          //go deep
          for (TreeNode child : m_children) {
              child.activate(clientID);
          }
  
      }
docs: Activate all topic subscriptions for the given clientID.