[sr-dev] calling module's functions in my custom module

Hi, I am trying to develop custom Kamailio module in C and I am wondering if Kamailio itself provide some kind of mechanism that allow me to call other modules functions. Most of the functions I need to call are defined as "static" and there are accessible only in kamailio.cfg file (eg. nathelper's 'fix_nated_sdp_f()'). Is there any chance that I can call these methods in my custom module? Or I need to use them only in kamailio.cfg and provide it with my module? Thank's for help in advance.