How to create a custom trigger?

[Shen Li]

Hi,

I created a custom trigger class (XYZ) by extending the OnceTrigger. During
execution, I got this error "Cannot translate trigger class XYZ to a
runner-API proto." It seems that the Triggers.ProtoConverter class needs to
declare a convertSpecific method for my trigger XYZ. How can I use my
custom trigger without modifying Beam's Triggers class?

Thanks,

Shen