[pacman-dev] alpm_option_set_logcb(), an example of usage

Hi, I'm developing pyalpm at the moment(new codebase, not related to 2005 pyalpm) and I don't really see any example of usage of alpm_option_set_logcb() on pacman.c file there is alpm_option_set_logcb(cb_log); but I can't find where is cb_log declared, so I have no clue about what does that function do(as I haven't neither found where is the actual code of that function, only that is declared on alpm.h)