code: public Integer getVarDataKey(FieldType type)
     {
        Integer result = null;
        FieldItem item = m_map.get(type);
        if (item != null)
        {
           result = item.getVarDataKey();
        }
        return result;
     }
docs: Retrieve the var data key for a specific field.
  
  @param type field type
  @return var data key