Topic: Builder::CSS usage

The Builder documentation [] lists a class to build a CSS style sheet. However, I don't see this file in my /usr/lib/gems/.../activesupport/.../builder/ directory. All of the other documented class files are there.

But even if it were there, I am unclear as to how it would be used. Should the file be stored in the public/stylesheets directory? Should it have an .rxml extension? How is it declared in the view template? Is it somehow included in the xml.head { ... } section of the template?