how to use regex with vega

Question

I am new to vega lite / vega.

I'm trying to write a regex query for a java log error as following with vega tree layout. A field 'message' contains :

[Poolthread] com.xxxx.content.core-bundle com.xxxxx.content.model.impl.RegisterTypeInternal(3179)] The activate method has thrown an exception (com.xxxxx.content.model.exception.ModelException: ModelException: {Code}-LCC-REP-FCT-002, {Message}-Access denied)
com.xxxx.content.model.exception.ModelException: ModelException: {Code}-LCC-REP-FCT-002, {Message}-Access denied
    at com.xxxxx.content.repository.utils.ExceptionUtil.getException(ExceptionUtil.java:52)
    at com.xxxxx.content.repository.utils.ExceptionUtil.getException(ExceptionUtil.java:171)

i'm use this regex which gets an exception word before the character : (like as ModelException ) but i don't how use this regex in vega . i tested this regex on the site regex101.com and it works fine.

([a-zA-Z0-9_]+)(?=:)

Thank for your help