public Builder addUpgradeLevels(org.bwapi.proxy.messages.GameMessages.UpgradeLevel value) {
        if (upgradeLevelsBuilder_ == null) {
          if (value == null) {
            throw new NullPointerException();
          }
          ensureUpgradeLevelsIsMutable();
          upgradeLevels_.add(value);
          onChanged();
        } else {
          upgradeLevelsBuilder_.addMessage(value);
        }
        return this;
      }