[fbsync] clarifying docs for ToPILImage() (#7679)

Summary: Co-authored-by: Nicolas Hug <[email protected]>

Reviewed By: vmoens

Differential Revision: D47186568

fbshipit-source-id: e18b4e33bd621d4c6b38bba3f6c6c405bad35cc5

Author: NicolasHug

torchvision/transforms/transforms.py

@@ -199,21 +199,21 @@ def forward(self, image):
 
 
 class ToPILImage:
-    """Convert a tensor or an ndarray to PIL Image - this does not scale values.
+    """Convert a tensor or an ndarray to PIL Image
 
     This transform does not support torchscript.
 
     Converts a torch.*Tensor of shape C x H x W or a numpy ndarray of shape
-    H x W x C to a PIL Image while preserving the value range.
+    H x W x C to a PIL Image while adjusting the value range depending on the ``mode``.
 
     Args:
         mode (`PIL.Image mode`_): color space and pixel depth of input data (optional).
             If ``mode`` is ``None`` (default) there are some assumptions made about the input data:
+
             - If the input has 4 channels, the ``mode`` is assumed to be ``RGBA``.
             - If the input has 3 channels, the ``mode`` is assumed to be ``RGB``.
             - If the input has 2 channels, the ``mode`` is assumed to be ``LA``.
-            - If the input has 1 channel, the ``mode`` is determined by the data type (i.e ``int``, ``float``,
-            ``short``).
+            - If the input has 1 channel, the ``mode`` is determined by the data type (i.e ``int``, ``float``, ``short``).
 
     .. _PIL.Image mode: https://pillow.readthedocs.io/en/latest/handbook/concepts.html#concept-modes
     """