I believe the RI output for YAML needs to be fixed to display more detailed information on usage. Currently, it displays nothing. I'm happy to start some documentation on the YAML const in lib/yaml.rb with any pointers in the right direction. View below for more information:
The YAML module allows you to use one of the two YAML engines that ship with
ruby. By default Psych is used but the old and unmaintained Syck may be
chosen.
This issue was solved with changeset r40499.
Lee, thank you for reporting this issue.
Your contribution to Ruby is greatly appreciated.
May Ruby be with you.
lib/yaml.rb: Documentation for YAML module [Bug #8213]