Remove Multi-threaded image conversion for fast image processors (#36105)

remove multithreaded image conversion

Co-authored-by: Marc Sun <57196510+SunMarc@users.noreply.github.com>

src/transformers/image_processing_utils_fast.py

@@ -13,7 +13,6 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
-from concurrent.futures import ThreadPoolExecutor
 from functools import lru_cache, partial
 from typing import Any, Dict, Iterable, List, Optional, Tuple, TypedDict, Union
 
@@ -497,8 +496,10 @@ class BaseImageProcessorFast(BaseImageProcessor):
             input_data_format=input_data_format,
             device=device,
         )
-        with ThreadPoolExecutor() as executor:
+        # todo: yoni - check if we can parallelize this efficiently
-            processed_images = list(executor.map(process_image_fn, images))
+        processed_images = []
+        for image in images:
+            processed_images.append(process_image_fn(image))
 
         return processed_images