How to add a new property type(integer) to StyleManager?

Hi, I am trying to create a custom StyleManager property with 'integer' type. My ultimate goal is to 're-define' how certain units are displayed. For example, the user use unit 'X' and then the actual value would be different in pixels.(One of the reasons is the new dragmode since it is using pixels, so I want to keep all values in pixels but would allow the user to use other units). I've checked the available functions and by extending the 'integer' number input I should be able to achieve that. But I get an error when I try to extend the 'integer' type. The code I tried: This gives an error...