mouse sensitivity problem

i want to know my current sensitivity and change it by numbers , not the slider bar.
the file which locates at [C:\Users\USERNAME\AppData\Roaming\Natural Selection 2\system_options.xml] used to show my mouse sensitivity setting , but it is not there anymore , only the fov setting left.
i also tried typing [i_sensitivity] in console to see or change my mouse sensitivity. however nothing happened.
the other commands like r_stats still works though , i wonder why [i_sensitivity] isnt working.