[Doc] Add Tensor.Shape

Summary:
Add `Tensor.Shape` doc.

Ref:

- pytorch#5544
- pytorch#1980

Differential Revision: D47278630

fbshipit-source-id: 823ee4776a8ef1086c3b37c3d1af3b5bb9355a1c

docs/source/tensors.rst

@@ -622,6 +622,7 @@ Tensor class reference
     Tensor.asinh_
     Tensor.arcsinh
     Tensor.arcsinh_
+    Tensor.shape
     Tensor.size
     Tensor.slogdet
     Tensor.slice_scatter

torch/_tensor_docs.py

@@ -4720,6 +4720,25 @@ def callable(a, b) -> number
 """,
 )
 
+add_docstr_all(
+    "shape",
+    r"""
+shape() -> torch.Size
+
+Returns the size of the :attr:`self` tensor. Tensor :attr:`shape` is the alias for :attr:`size`.
+It was added for consistency with NumPy.
+
+Example::
+
+    >>> t = torch.empty(3, 4, 5)
+    >>> t.size()
+    torch.Size([3, 4, 5])
+    >>> t.shape
+    torch.Size([3, 4, 5])
+
+""",
+)
+
 add_docstr_all(
     "sort",
     r"""