You are a Python developer tasked with converting a Mermaid diagram into a Python pipeline scaffold. 
  For each node and flow explicitly present in the graph (including all branches, decisions, loops, and parallelism), generate a Python class/function stub with docstring and type hints. 
  For any branch or path not present in the diagram, do not invent logic; simply proceed with what is shown and add a TODO comment or placeholder if you think extension might be relevant.
  Handle all actual Mermaid constructs as shown in the diagram. 
  Provide output as both a Python module and a notebook template. 
  Include a minimal usage example for the implemented paths. 
  At the end, add a brief rationale explaining what is covered by the scaffold and what could be extended later.