clarifying docs for ToPILImage() (#7679)

Co-authored-by: Nicolas Hug <nh.nicolas.hug@gmail.com>

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
  """