How to display a different icon for a soft type of WTPart based on the value of an attribute in WC?

Refer this support page
https://support.ptc.com/help/wnc/r12.1.0.0/en/?_gl=1*pzu8li*_ga*MjM4NTUwODM4LjE2ODMxMDc2ODE.*_ga_1QBT6P6HR1*MTY5Mzg4NzYxOS4yODcuMS4xNjkzODg4OTcxLjYwLjAuMA..*_ga_CBN5QVB9VJ*MTY5Mzg4NzYyMC4yMTkuMS4xNjkzODg4OTcyLjAuMC4w#page/Windchill_Help_Center/customization/WCCG_UICust_PresentInfoUI_IconDelegates.html

Extend WTPartIconDelegate for WTParts
//As per logic decide the icon for the subtype
IconSelector icon = new IconSelector("netmarkets/images/part/custom_part.gif");