Complete magnet holder navigation (#373)

[gupichon]

Description

Extends MagnetsHolder with a get_cfm() shortcut to fetch all combined-function magnets, and adds dynamic attribute access for configured array names (e.g. magnets.QuadForTune instead of magnets.get("QuadForTune")) across all GenericArrayHolder-based holders (MagnetsHolder, CombinedFunctionMagnetsHolder, SerializedMagnetsHolder, BPMsHolder). dir() is also extended so interactive completion (IPython/Jupyter) proposes configured array names.

Related Issue

• Fixes Feature: Complete magnet holder navigation #373

Features/issues described there are:

• new feature: magnets.get_cfm() was added, delegating to the existing combined_function_magnets.get() — no new array-construction logic.
• new feature: dynamic attribute access was implemented as GenericArrayHolder.__getattr__, generalized to the base class (broader scope than requested in the issue) rather than only MagnetsHolder, since the same navigation is useful on CombinedFunctionMagnetsHolder/SerializedMagnetsHolder/BPMsHolder and the mechanism is identical. __getattr__ only triggers on lookup failure, so it never shadows get/add/private attributes, and raises AttributeError for unknown or non-identifier names.

Changes to existing functionality

• None. GenericArrayHolder/GenericElementHolder had no prior __getattr__/__dir__; existing attribute/method resolution is unaffected since __getattr__ only runs after normal lookup fails.

Testing

The following tests (compatible with pytest) were added:

• tests/common/test_array_holder_navigation.py:
  • dynamic attribute returns the same array as get(), for MagnetsHolder, CombinedFunctionMagnetsHolder, BPMsHolder, and SerializedMagnetsHolder
  • unknown array name raises AttributeError
  • dynamic access does not shadow existing methods (get, add)
  • a non-identifier array name is rejected and excluded from dir()
  • dir() includes configured array names for completion
  • get_cfm() returns a CombinedFunctionMagnetArray matching combined_function_magnets.get()
  • test_issue_373_example: reproduces the issue's example code verbatim against real test-lattice data (tests/config/EBSTune-patterns.yaml)
• tests/test_load_conf_with_code.py: one extra assertion exercising dynamic attribute access end-to-end (sr.live.bpms.BPM)

Verify that your checklist complies with the project

• New and existing unit tests pass locally (315 passed, 1 pre-existing unrelated failure: tests/tuning_tools/test_tuning_orm.py, a Windows-only NamedTemporaryFile double-open issue, unaffected by this change)
• Tests were added to prove that all features/changes are effective
• The code is commented where appropriate (NumPy-style docstrings on all new/changed public API, including class-level docstrings so the dynamic attribute access is discoverable via help())
• Any existing features are not broken