[Misc] Add SPDX-License-Identifier headers to python source files (#12628)

- **Add SPDX license headers to python source files**
- **Check for SPDX headers using pre-commit**

commit 9d7ef44c3cfb72ca4c32e1c677d99259d10d4745
Author: Russell Bryant <rbryant@redhat.com>
Date:   Fri Jan 31 14:18:24 2025 -0500

    Add SPDX license headers to python source files
    
This commit adds SPDX license headers to python source files as
recommended to
the project by the Linux Foundation. These headers provide a concise way
that is
both human and machine readable for communicating license information
for each
source file. It helps avoid any ambiguity about the license of the code
and can
    also be easily used by tools to help manage license compliance.
    
The Linux Foundation runs license scans against the codebase to help
ensure
    we are in compliance with the licenses of the code we use, including
dependencies. Having these headers in place helps that tool do its job.
    
    More information can be found on the SPDX site:
    
    - https://spdx.dev/learn/handling-license-info/

Signed-off-by: Russell Bryant <rbryant@redhat.com>

commit 5a1cf1cb3b80759131c73f6a9dddebccac039dea
Author: Russell Bryant <rbryant@redhat.com>
Date:   Fri Jan 31 14:36:32 2025 -0500

    Check for SPDX headers using pre-commit
Signed-off-by: Russell Bryant <rbryant@redhat.com>

---------
Signed-off-by: Russell Bryant <rbryant@redhat.com>

tests/samplers/test_beam_search.py

+# SPDX-License-Identifier: Apache-2.0
 """Compare the outputs of HF and vLLM when using beam search.
 
 Run `pytest tests/samplers/test_beam_search.py`.

tests/samplers/test_ignore_eos.py

+# SPDX-License-Identifier: Apache-2.0
 """Make sure ignore_eos works.
 
 Run `pytest tests/samplers/test_ignore_eos.py`.

tests/samplers/test_logits_processor.py

+# SPDX-License-Identifier: Apache-2.0
+
 import pytest
 import torch
 

tests/samplers/test_logprobs.py

+# SPDX-License-Identifier: Apache-2.0
+
 from typing import List
 
 import pytest

tests/samplers/test_no_bad_words.py

+# SPDX-License-Identifier: Apache-2.0
 """Make sure bad_words works.
 
 Run `pytest tests/samplers/test_no_bad_words.py`.

tests/samplers/test_ranks.py

+# SPDX-License-Identifier: Apache-2.0
+
 import pytest
 
 from vllm import SamplingParams

tests/samplers/test_rejection_sampler.py

+# SPDX-License-Identifier: Apache-2.0
 """Tests for rejection sampling."""
 from typing import List, Tuple
 

tests/samplers/test_sampler.py

+# SPDX-License-Identifier: Apache-2.0
+
 import itertools
 import random
 from dataclasses import dataclass

tests/samplers/test_seeded_generate.py

+# SPDX-License-Identifier: Apache-2.0
 """Verify that seeded random sampling is deterministic.
 
 Run `pytest tests/samplers/test_seeded_generate.py`.

tests/samplers/test_typical_acceptance_sampler.py

+# SPDX-License-Identifier: Apache-2.0
 """Tests for rejection sampling."""
 
 import pytest

tests/spec_decode/e2e/conftest.py

+# SPDX-License-Identifier: Apache-2.0
+
 from itertools import cycle
 from typing import List, Optional, Sequence, Tuple, Union
 

tests/spec_decode/e2e/test_compatibility.py

+# SPDX-License-Identifier: Apache-2.0
+
 import pytest
 
 from vllm import SamplingParams

tests/spec_decode/e2e/test_eagle_correctness.py

+# SPDX-License-Identifier: Apache-2.0
 """This docstring details important information on the testing methodology.
 
 Most of the tests rely on "greedy equality", where we expect the output of

tests/spec_decode/e2e/test_integration.py

+# SPDX-License-Identifier: Apache-2.0
 """Tests which cover integration of the speculative decoding framework with
 other features, e.g. cuda graphs.
 """

tests/spec_decode/e2e/test_integration_dist_tp2.py

+# SPDX-License-Identifier: Apache-2.0
 """Tests which cover integration of the speculative decoding framework with
 tensor parallelism.
 """

tests/spec_decode/e2e/test_integration_dist_tp4.py

+# SPDX-License-Identifier: Apache-2.0
 """Tests which cover integration of the speculative decoding framework with
 tensor parallelism.
 """

tests/spec_decode/e2e/test_logprobs.py

+# SPDX-License-Identifier: Apache-2.0
+
 from itertools import cycle
 
 import pytest

tests/spec_decode/e2e/test_medusa_correctness.py

+# SPDX-License-Identifier: Apache-2.0
 """This docstring details important information on the testing methodology.
 
 Most of the tests rely on "greedy equality", where we expect the output of

tests/spec_decode/e2e/test_mlp_correctness.py

+# SPDX-License-Identifier: Apache-2.0
 """This docstring details important information on the testing methodology.
 
 Most of the tests rely on "greedy equality", where we expect the output of

tests/spec_decode/e2e/test_multistep_correctness.py

+# SPDX-License-Identifier: Apache-2.0
 """The tests in this file verify end-to-end speculative decoding correctness.
 
 This docstring details important information on the testing methodology.