Plugin Development - certificate() not available ,why?

Questions
1

kong version:0.14.1

function CustomHandler:certificate(config)
– Eventually, execute the parent implementation
– (will log that your plugin is entering this context)
CustomHandler.super.certificate(self)

– Implement any custom logic here
end

2

my demand: dynamic set ssl_protocols TLSv1 TLSv1.1 TLSv1.2 by certificate SNI