Edward Loper 151c540727 Fix issue where tf.ragged.stack([tensor]) would return a Tensor rather than a RaggedTensor.
Also updated docs to clarify that the result will be a `Tensor` if the rank of result is 1 (since `RaggedTensor` can only be used when `rank>1`).  E.g., `tf.ragged.stack([1, 2, 3])` returns a 1D `Tensor`, not a `RaggedTensor`.

PiperOrigin-RevId: 357983061
Change-Id: I41b69f395142162357bcd8d7385221b5fb2267c1
2021-02-17 10:49:01 -08:00
..
2021-01-20 17:11:44 -08:00