Calling user-defined events by API

I have defined a user defined event, how can I call it by using API ?

TriggerCommand: https://doc.developer.milestonesys.com/html/index.html?base=miphelp/class_video_o_s_1_1_platform_1_1_messaging_1_1_message_id_1_1_control.html&tree=tree_search.html?search=triggercommand

It can be seen in use if you explore the Message Tester plugin sample..

https://doc.developer.milestonesys.com/html/index.html?base=samples/pluginsamples/messagetester/readme.html&tree=tree_1.html

https://github.com/milestonesys