'clear' can be used only in on load actions (deluge error message)

'clear' can be used only in on load actions (deluge error message)

But In the following page: h ttps://www.zoho.com/creator/help/fields/add-to-picklist-dynamically.html 
you say:

Example

Below is an example code that can be specified in the On User Input action of a subform picklist field.

list = Product [Category == row.Category] sort by Product_Code ;
clear row.Items;
row.Items:UI.append(itemlist.Product_Code.getall())