pipe node decorator

[jucordero]

Description

This PR addresses #96 by adding a decorator which converts arbitrary functions into node functions which can work inside a pipeline

Checklist

• Follow the Contributor Guidelines
• Write documentation strings
• Write unit tests

[Copilot]

Pull request overview

Adds a pipeline_node decorator intended to wrap regular Python functions so they can be executed as pipeline nodes (reading inputs from a datablock and writing outputs back), addressing issue #96.

Changes:

• Introduces pipeline_node decorator in pipeline.py using get_dict/set_dict datablock helpers.
• Fixes Pipeline.add_node to avoid a mutable default argument (params={} → params=None).
• Updates pipeline tests and package exports to reflect the new decorator/import patterns.

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated 6 comments.

File	Description
agrifoodpy/pipeline/pipeline.py	Adds pipeline_node, imports get_dict/set_dict, and fixes add_node default params handling.
agrifoodpy/pipeline/tests/test_pipeline.py	Adds unit tests covering pipeline_node behavior (single/multiple inputs, return key, external function, error cases) and adjusts imports.
agrifoodpy/pipeline/__init__.py	Changes re-exports (drops dict_utils wildcard export; keeps pipeline exports).

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[Copilot]

In pipeline mode the wrapper calls func(**pipeline_kwargs). This will fail for arbitrary functions that have positional-only parameters (common in builtins and some C-extension APIs), which undermines the stated goal of supporting external functions. A more robust approach is to update the existing bound.arguments values for input_keys and then invoke func(*bound.args, **bound.kwargs) so positional-only parameters are passed correctly.

Suggested change

	pipeline_kwargs = dict(bound.arguments)
	for key in input_keys:
	pipeline_kwargs[key] = get_dict(datablock,
	pipeline_kwargs[key])
	result = func(**pipeline_kwargs)
	for key in input_keys:
	bound.arguments[key] = get_dict(datablock,
	bound.arguments[key])
	result = func(*bound.args, **bound.kwargs)