Nodes

A node is one step in the pipeline graph. Every node has an id (the tool name, suffixed _1, _2, … if the same tool is added more than once) and a list of upstream nodes (inNodes) populated by add_edge().

There are six kinds:

Node	Constructor	Role
Input	add_input_node(**values)	Holds user-supplied file paths and scalar parameters. Runs no tool.
Tool	add_node(name)	Wraps one registry tool; runs once per execution.
Gather	add_gather_node(name, split_key=...)	Runs a one-input tool once per item of an upstream collection, then gathers.
Decision	add_decision_node(score_fn, conditions, modifier_tool)	Re-runs an upstream until a scored condition holds (bounded feedback loop).
Output	set_output_node(node)	Marks the node whose result execute() returns.
Subgraph	SubGraph()	A one-in / one-out pipeline usable as a single node.