Update pipeline API to accept arbitrary sequence of Tensors and not just Tuple

[pritamdamania87]

Stack from ghstack:

• Test pipeline parallelism works with DDP. #48470 Test pipeline parallelism works with DDP.
• Update pipeline API to accept arbitrary sequence of Tensors and not just Tuple #48467 Update pipeline API to accept arbitrary sequence of Tensors and not just Tuple

The current API's forward method only accepted a Tensor or a Tuple of
Tensors, making this more generic by accepting any Sequence of Tensors.

Differential Revision: D25181944

[dr-ci]

💊 CI failures summary and remediations

As of commit 9f84d16 (more details on the Dr. CI page):

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• 1/1 failures introduced in this PR

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🕵️ 1 new failure recognized by patterns

The following CI failures do not appear to be due to upstream breakages:

pytorch_linux_xenial_py3_6_gcc5_4_test (1/1)

Step: "Run tests" (full log | diagnosis details | 🔁 rerun)

Dec 12 00:00:30 AssertionError: mypy failed: tools/codegen/gen.py:388:9: error: Missing return statement

Dec 12 00:00:08   test_run_mypy (__main__.TestTypeHints) ... ok (58.625s)
Dec 12 00:00:11   test_run_mypy_strict (__main__.TestTypeHints) ... FAIL (2.755s)
Dec 12 00:00:30   test_type_hint_examples (__main__.TestTypeHints) ... ok (19.286s)
Dec 12 00:00:30 
Dec 12 00:00:30 ======================================================================
Dec 12 00:00:30 FAIL [2.755s]: test_run_mypy_strict (__main__.TestTypeHints)
Dec 12 00:00:30 ----------------------------------------------------------------------
Dec 12 00:00:30 Traceback (most recent call last):
Dec 12 00:00:30   File "test_type_hints.py", line 239, in test_run_mypy_strict
Dec 12 00:00:30     self.fail(f"mypy failed: {stdout} {stderr}")
Dec 12 00:00:30 AssertionError: mypy failed: tools/codegen/gen.py:388:9: error: Missing return statement
Dec 12 00:00:30 Found 1 error in 1 file (checked 11 source files)
Dec 12 00:00:30  
Dec 12 00:00:30 
Dec 12 00:00:30 ----------------------------------------------------------------------
Dec 12 00:00:30 Ran 4 tests in 91.234s
Dec 12 00:00:30 
Dec 12 00:00:30 FAILED (failures=1)
Dec 12 00:00:30 
Dec 12 00:00:30 Generating XML reports...
Dec 12 00:00:30 Generated XML report: test-reports/dist-gloo/TEST-TestTypeHints-20201211235859.xml

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This comment has been revised 51 times.

[rohan-varma]

LGTM

[facebook-github-bot]

This pull request has been merged in dc4db95.