Hi,
Ok, I see !
We don't provide example because you have to copy the code from the indicated file.
In the case of the function "hikashop_image_toggle_js", it is the helper image file.
When you open it, you can search for the text "hikashop_image_toggle_js" in the file and you will see the default javascript content include in the helper file.
The override is just a simple php file with a function which will return some "text", you can copy paste the javascript content in the helper image file as the base.
This override will be improved, we are currently working on a new image system for HikaShop.
Regards,
Jerome - Obsidev.com
HikaMarket & HikaSerial developer / HikaShop core dev team.
Also helping the HikaShop support team when having some time or couldn't sleep.
By the way, do not send me private message, use the "contact us" form instead.