Prior to that you need to make sure that , the attachments of the parent case should get populated on to the childWO thread in the clipboard
This is my Parent workobject : for which I have added one attachment
Below is my child case : for which i have added an other attachment
If we check the clipboard of the parent wo : both the child and parent case attachments got populated :
where as for child case : Only child case attachment is present on the clipboard :
Therefore : to display the parent case attachments into the child case WO , first we need to make sure that parent case attachments gets populated on the clipboard, then need to customize the pyCaseAttachment section .