```ruby
module YARD  #:nodoc: all
  class Docstring
    include Yardstick::Method
  end # class Docstring
end # module YARD
```

Add description for extension class
user
```ruby
module YARD  #:nodoc: all

  # Extend docstring with yardstick methods
  class Docstring
    include Yardstick::Method
  end # class Docstring
end # module YARD
```
assistant