code: public void addLabel(Label label)
      {
          // Add the label to any applications it is associated with
          List<Long> applicationIds = label.getLinks().getApplications();
          for(long applicationId : applicationIds)
          {
              Application application = applications.get(applicationId);
              if(application != null)
                  labels(applicationId).add(label);
              else
                  logger.severe(String.format("Unable to find application for label '%s': %d", label.getKey(), applicationId));
          }
      }
docs: Adds the label to the applications for the account.
  @param label The label to add