YPath not supported yet. (NotImplementedError)

[GETandSELECT]

Hey

I don't know if a usage error or missing feature. Do I use it correct?

yaml sort  xxx-targets.yml
Traceback (most recent call last):
	4: from /usr/local/bin/yaml:6:in `<main>'
	3: from /usr/local/bin/yaml:6:in `load'
	2: from /usr/local/Cellar/gem-yaml_command/0.1.1/gems/yaml_command-0.1.1/bin/yaml:4:in `<top (required)>'
	1: from /usr/local/Cellar/gem-yaml_command/0.1.1/gems/executable-1.2.1/lib/executable/domain.rb:100:in `execute'
/usr/local/Cellar/gem-yaml_command/0.1.1/gems/yaml_command-0.1.1/lib/yaml_command/sort.rb:22:in `call': YPath not supported yet. (NotImplementedError)