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torchvision/transforms/v2/functional/_color.py

@@ -79,11 +79,13 @@ def grayscale_to_rgb(inpt: torch.Tensor) -> torch.Tensor:
 @_register_kernel_internal(grayscale_to_rgb, torch.Tensor)
 @_register_kernel_internal(grayscale_to_rgb, tv_tensors.Image)
 def grayscale_to_rgb_image(image: torch.Tensor) -> torch.Tensor:
+    # rgb_to_grayscale can be used to add channels so we reuse that function.
     return _rgb_to_grayscale_image(image, num_output_channels=3, preserve_dtype=True)
 
 
 @_register_kernel_internal(grayscale_to_rgb, PIL.Image.Image)
 def grayscale_to_rgb_image_pil(image: PIL.Image.Image) -> PIL.Image.Image:
+    # to_grayscale can expand channels from 1 to 3 so we reuse that function.
     return _FP.to_grayscale(image, num_output_channels=3)