The plugin registry

Implement collect_plugins(registry, group) — registry maps group names to lists of (package, plugin_name, factory) tuples: - returns {plugin_name: factory} for that group - a duplicate plugin name raises ValueError('duplicate plugin: <name>') — silent shadowing is how plugin bugs hide - factories are returned, never called This is the entry-points mechanism (and the Module-2 registry) in miniature.

Difficulty: advanced