not able to find to_yaml definition

I am looking at rails edge source code.

I am able to do

puts User.find.to_yaml

However I am not able to find piece of code where 'def to_yaml' is. How this to_yaml serialization is working?

can fully understand how to_json and to_xml is working but to_yaml beats me.

Thanks

YAML is part of Ruby. Check out Index of Files, Classes & Methods in Ruby 3.1.2 (Ruby 3.1.2) for YAML class readme.

rick