@Override
    public String calcLabel(ValueDescriptor descriptor, EvaluationContext evaluationContext, DescriptorLabelListener listener)
      throws EvaluateException {
      if (!isShowValue(descriptor, evaluationContext)) {
        descriptor.putUserData(RENDERER_MUTED, true);
        return "";
      }
      String keyText = calcExpression(evaluationContext, descriptor, myKeyExpression, listener, KEY_DESCRIPTOR);
      String valueText = calcExpression(evaluationContext, descriptor, myValueExpression, listener, VALUE_DESCRIPTOR);
      return keyText + " -> " + valueText;
    }
@Override
    public String calcLabel(ValueDescriptor descriptor, EvaluationContext evaluationContext, DescriptorLabelListener listener)