"after" custom transformer seems to be called before the JS transformation.

Hi there,

I am trying to implement an after custom transformer as I am planning to make changes to the transpiled JS code.
According to the inline documentation (Custom transformers to evaluate after built-in .js transformations.), the transformer should be called after the source file is transpiled to JS. In the transformer API, the only provided argument is a "SourceFile" object which has no reference to the JS code (or at least I couldn't find it).

What's the point of having an after transformer if you don't get access to the transformed source code, nor have possibilities to change it? Is it a bug or is it like that on purpose?

Thanks in advance