Add utility function for retrieving locally cached models (#8836)

* add get_cached_models function

* add List type to import

* fix code quality

* Update src/transformers/file_utils.py
Co-authored-by: Sylvain Gugger <35901082+sgugger@users.noreply.github.com>

* Update src/transformers/file_utils.py
Co-authored-by: Sylvain Gugger <35901082+sgugger@users.noreply.github.com>

* Update src/transformers/file_utils.py
Co-authored-by: Sylvain Gugger <35901082+sgugger@users.noreply.github.com>

* Update src/transformers/file_utils.py
Co-authored-by: Sylvain Gugger <35901082+sgugger@users.noreply.github.com>

* Update src/transformers/file_utils.py
Co-authored-by: Sylvain Gugger <35901082+sgugger@users.noreply.github.com>

* Fix style
Co-authored-by: Sylvain Gugger <35901082+sgugger@users.noreply.github.com>

src/transformers/file_utils.py

@@ -32,7 +32,7 @@ from dataclasses import fields
 from functools import partial, wraps
 from hashlib import sha256
 from pathlib import Path
-from typing import Any, BinaryIO, Dict, Optional, Tuple, Union
+from typing import Any, BinaryIO, Dict, List, Optional, Tuple, Union
 from urllib.parse import urlparse
 from zipfile import ZipFile, is_zipfile
 
@@ -1030,6 +1030,39 @@ def filename_to_url(filename, cache_dir=None):
     return url, etag
 
 
+def get_cached_models(cache_dir: Union[str, Path] = None) -> List[Tuple]:
+    """
+    Returns a list of tuples representing model binaries that are cached locally. Each tuple has shape
+    :obj:`(model_url, etag, size_MB)`. Filenames in :obj:`cache_dir` are use to get the metadata for each model, only
+    urls ending with `.bin` are added.
+
+    Args:
+        cache_dir (:obj:`Union[str, Path]`, `optional`):
+            The cache directory to search for models within. Will default to the transformers cache if unset.
+
+    Returns:
+        List[Tuple]: List of tuples each with shape :obj:`(model_url, etag, size_MB)`
+    """
+    if cache_dir is None:
+        cache_dir = TRANSFORMERS_CACHE
+    elif isinstance(cache_dir, Path):
+        cache_dir = str(cache_dir)
+
+    cached_models = []
+    for file in os.listdir(cache_dir):
+        if file.endswith(".json"):
+            meta_path = os.path.join(cache_dir, file)
+            with open(meta_path, encoding="utf-8") as meta_file:
+                metadata = json.load(meta_file)
+                url = metadata["url"]
+                etag = metadata["etag"]
+                if url.endswith(".bin"):
+                    size_MB = os.path.getsize(meta_path.strip(".json")) / 1e6
+                    cached_models.append((url, etag, size_MB))
+
+    return cached_models
+
+
 def cached_path(
     url_or_filename,
     cache_dir=None,