unity How to detect when HoloLens is worn

[wechat_os_Qy073_Y_0_JJtEXnhpP0SdH6Y]

my environment:
unity2020.3.20f1c1
use xr plugin management
mrtk2.7.3
hololens2
visual studio2019

thanks.

[wechat_os_Qy073_Y_0_JJtEXnhpP0SdH6Y]

help!!!