fails:YAML.dump converts an object to YAML and write result to io when io provided
fails:YAML.dump returns a string containing dumped YAML when no io provided
fails:YAML.dump returns the same string that #to_yaml on objects
fails:YAML.dump dumps strings into YAML strings
fails:YAML.dump dumps hashes into YAML key-values
fails:YAML.dump dumps Arrays into YAML collection
