How to reference to a class within a static method? 

```
class Car
  def self.new_from_xml(xml)
    instance = self.class.new
    #do some stuff with xml
    instance
  end
end

class Mercedes < Car
end

class Porsche < Car
end

```

IRB:

```
Mercedes.new_from_xml(somedata) # Output is #<Class:...>, should be #<Mercedes:...>
Porsche.new_from_xml(somedata)  # Output is #<Class:...>, should be #<Porsche:...>

```