Other posters correctly described _what_ this is, but I didn't see anyone answer _why_. Using a Symbol as the method name disambiguates this method from any pr

Other posters correctly described _what_ this is, but I didn't see anyone answer _why_. Using a Symbol as the method name disambiguates this method from any previously-defined methods. In other words, by using a Symbol for the method name (and not using a string), it's impossible to "name collide" on this new API, which would accidentally mark a class as disposable.