A great YAML library for ruby?

Could anyone suggest a well-documented and well known YAML library for ruby?

A book I read used one like this:

YAML.load_file(conf.rc).each do |k,v|
  conf.send("#{k}=", v)
end

Anyone know which library is used?

Thanks

It's party of the standard library. Just put

require 'yaml'

in your file and you can use it. Read more here.