code: private String getCustomFieldOutlineCodeValue(Var2Data varData, Var2Data outlineCodeVarData, Integer id)
     {
        String result = null;
  
        int uniqueId = id.intValue();
        if (uniqueId == 0)
        {
           return "";
        }
  
        CustomFieldValueItem item = m_file.getCustomFields().getCustomFieldValueItemByUniqueID(uniqueId);
        if (item != null)
        {
           Object value = item.getValue();
           if (value instanceof String)
           {
              result = (String) value;
           }
  
           if (result != null && !NumberHelper.equals(id, item.getParent()))
           {
              String result2 = getCustomFieldOutlineCodeValue(varData, outlineCodeVarData, item.getParent());
              if (result2 != null && !result2.isEmpty())
              {
                 result = result2 + "." + result;
              }
           }
        }
  
        return result;
     }
docs: Retrieve custom field value.
  
  @param varData var data block
  @param outlineCodeVarData var data block
  @param id parent item ID
  @return item value