fix: Expose cache_clear method for _manifests function

- Create explicit cache instance for _manifests
- Add cache_clear attribute to enable cache clearing in tests
- Remove type: ignore comment as cache_clear is now properly exposed
- Fixes CI/CD mypy unused-ignore error

Author: ForeverAngry

pyiceberg/manifest.py

@@ -876,13 +876,22 @@ def __hash__(self) -> int:
         return hash(self.manifest_path)
 
 
-@cached(cache=LRUCache(maxsize=128), key=lambda io, manifest_list: hashkey(manifest_list), lock=threading.RLock())
+# Create cache instance for _manifests function
+_manifests_cache: LRUCache[Tuple[str, str], Tuple[ManifestFile, ...]] = LRUCache(maxsize=128)
+_manifests_lock = threading.RLock()
+
+
+@cached(cache=_manifests_cache, key=lambda io, manifest_list: hashkey(manifest_list), lock=_manifests_lock)
 def _manifests(io: FileIO, manifest_list: str) -> Tuple[ManifestFile, ...]:
     """Read and cache manifests from the given manifest list, returning a tuple to prevent modification."""
     file = io.new_input(manifest_list)
     return tuple(read_manifest_list(file))
 
 
+# Expose cache_clear method for testing
+_manifests.cache_clear = _manifests_cache.clear  # type: ignore[attr-defined]
+
+
 def read_manifest_list(input_file: InputFile) -> Iterator[ManifestFile]:
     """
     Read the manifests from the manifest list.

tests/utils/test_manifest.py

@@ -48,7 +48,7 @@
 @pytest.fixture(autouse=True)
 def clear_global_manifests_cache() -> None:
     # Clear the global cache before each test
-    _manifests.cache_clear()  # type: ignore[attr-defined]
+    _manifests.cache_clear()
 
 
 def _verify_metadata_with_fastavro(avro_file: str, expected_metadata: Dict[str, str]) -> None: