get_stock_id
Description:
Warning: get_stock_id is deprecated since 3.10.
Gets a stock id of an icon used by this attributes.
Note: 
      
        
    
    Don't use this function.
 Note that the stock id can be null if it wasn't set earlier.
Parameters:
| this | 
Returns:
| Stock id. Returned string is owned by this and shouldn't be freed. |