Ohai <plugin_name> command comes with an error


I just created ohai plugin.
I put the plugin under /etc/chef/ohai/plugins directory.

When I run ohai the data shows up at the bottom.
However when I run ohai <plugin_name> it comes with the error.

The error is:
`attributes_print’: I cannot find an attribute named <plugin_name>! (ArgumentError)

Did I miss something?