Code assumes that any SourceDataProvider has `key_selector`; This is not the case/not enforced: "object has no attribute 'key_selector'"

[hf-kklein]

bo4e_migration_framework/src/bomf/filter/sourcedataproviderfilter.py

Line 85 in e1a6740

key_selector_to_be_used = source_data_provider.key_selector # type:ignore[attr-defined]

Turns out the mypy warning is correct.

key_selector_to_be_used = source_data_provider.key_selector # type:ignore[attr-defined]
E AttributeError: 'MyOwnSourceDataProvider' object has no attribute 'key_selector'

reported by @hf-krechan