[NTG-context] How to set a empty string in texmf.cnf

Hi everyone, I need to set all SELFAUTOPARENT in texmf.cnf to empty string, but I don't know how. Here are what I have tried: SELFAUTOPARENT = SELFAUTOPARENT = "" SELFAUTOPARENT = '' SELFAUTOPARENT = $ SELFAUTOPARENT = ${} SELFAUTOPARENT = {} Although deleting all the SELFAUTOPARENT in texmf.cnf works, I just want my texmf.cnf more elegant :) Thanks in advance! Best wishes, Wei-Wei