I mean to use a function decorated with 

PipelineDecorator.pipeline

 inside another pipeline decorated in the same way.

Ohh... so would it make sense to add "helper_functions" so that a function will be available in the step's context ?
Or maybe we need a new to support "standalone" decorator?! Currently to actually "launch" the function step, you have to call it from the "pipeline" main logic function, but, at least in theory, one could do without the Pipeline itself... I really like this idea 🙂
Let me check a few things ...