Stop adiftools import from overriding notebook matplotlib backend

[Copilot]

Importing adiftools.adiftools in Kaggle/Jupyter disabled inline plotting because adifgraph changed matplotlib’s global backend to Agg at import time. This PR removes that import side effect so notebook plotting remains functional after importing the library.

• Backend behavior

  • Removed import-time backend override from adiftools/adifgraph.py:
    • deleted matplotlib.use('Agg')
    • removed now-unused import matplotlib
  • adiftools no longer mutates global matplotlib backend during import.

• Regression coverage

  • Added a focused test in tests/test_adifgraph.py to assert adifgraph import does not call matplotlib.use.

def test_import_does_not_force_matplotlib_backend(monkeypatch):
    calls = []

    def spy_use(*args, **kwargs):
        calls.append((args, kwargs))

    monkeypatch.setattr(matplotlib, 'use', spy_use)
    importlib.reload(adifgraph)

    assert calls == []

[Copilot]

Pull request overview

This PR removes an import-time matplotlib side effect from adiftools.adifgraph so importing the library no longer forces the global backend to Agg, which preserves inline plotting behavior in notebook environments.

Changes:

• Removed the import-time matplotlib.use('Agg') call and the now-unused matplotlib import from adiftools/adifgraph.py.
• Added a regression test that reloads adifgraph and asserts it does not call matplotlib.use.
• Kept the change narrowly scoped to backend side effects and their coverage.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated no comments.

File	Description
adiftools/adifgraph.py	Removes the module-level backend override that was mutating matplotlib state during import.
tests/test_adifgraph.py	Adds a regression test verifying adifgraph import/reload no longer invokes matplotlib.use.

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