Fix reduce-labels in BEIT Fast Image Processor (#38042)

* Fixed reduce-labels

* Little doc fix

* Change docstring

docs/source/en/model_doc/beit.md

@@ -150,6 +150,7 @@ If you're interested in submitting a resource to be included here, please feel f
 [[autodoc]] BeitImageProcessor
     - preprocess
     - post_process_semantic_segmentation
+
 ## BeitImageProcessorFast
 
 [[autodoc]] BeitImageProcessorFast

docs/source/ja/model_doc/beit.md

@@ -105,6 +105,7 @@ BEiT の使用を開始するのに役立つ公式 Hugging Face およびコミ
 
 [[autodoc]] BeitImageProcessor
     - preprocess
+    - post_process_semantic_segmentation
 
 ## BeitImageProcessorFast
 

src/transformers/models/beit/image_processing_beit_fast.py

@@ -137,12 +137,22 @@ class BeitImageProcessorFast(BaseImageProcessorFast):
         processed_images = torch.stack(processed_images, dim=0) if return_tensors else processed_images
         return processed_images
 
+    def _preprocess_images(
+        self,
+        images,
+        **kwargs,
+    ):
+        """Preprocesses images."""
+        kwargs["do_reduce_labels"] = False
+        processed_images = self._preprocess(images=images, **kwargs)
+        return processed_images
+
     def _preprocess_segmentation_maps(
         self,
         segmentation_maps,
         **kwargs,
     ):
-        """Preprocesses a single segmentation map."""
+        """Preprocesses segmentation maps."""
         processed_segmentation_maps = []
         for segmentation_map in segmentation_maps:
             segmentation_map = self._process_image(
@@ -215,7 +225,7 @@ class BeitImageProcessorFast(BaseImageProcessorFast):
         kwargs.pop("default_to_square")
         kwargs.pop("data_format")
 
-        images = self._preprocess(
+        images = self._preprocess_images(
             images=images,
             **kwargs,
         )