[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>

vllm/model_executor/guided_decoding/xgrammar_decoding.py

+# SPDX-License-Identifier: Apache-2.0
+
 # noqa: UP007
 from __future__ import annotations
 

vllm/model_executor/layers/activation.py

+# SPDX-License-Identifier: Apache-2.0
 """Custom activation functions."""
 import math
 from typing import Optional

vllm/model_executor/layers/fused_moe/__init__.py

+# SPDX-License-Identifier: Apache-2.0
+
 from contextlib import contextmanager
 from typing import Any, Dict, Optional
 

vllm/model_executor/layers/fused_moe/fused_marlin_moe.py

+# SPDX-License-Identifier: Apache-2.0
 """Fused MoE utilities for GPTQ."""
 import functools
 from typing import Optional

vllm/model_executor/layers/fused_moe/fused_moe.py

+# SPDX-License-Identifier: Apache-2.0
 """Fused MoE kernel."""
 import functools
 import json

vllm/model_executor/layers/fused_moe/layer.py

+# SPDX-License-Identifier: Apache-2.0
+
 from abc import abstractmethod
 from enum import Enum
 from typing import Callable, List, Optional, Tuple

vllm/model_executor/layers/fused_moe/moe_pallas.py

+# SPDX-License-Identifier: Apache-2.0
+
 import torch
 import torch.nn.functional as F
 from torch_xla.experimental.custom_kernel import _histogram

vllm/model_executor/layers/fused_moe/moe_torch_iterative.py

+# SPDX-License-Identifier: Apache-2.0
+
 import torch
 import torch.nn.functional as F
 

vllm/model_executor/layers/layernorm.py

+# SPDX-License-Identifier: Apache-2.0
 """Custom normalization layers."""
 from typing import Optional, Tuple, Union
 

vllm/model_executor/layers/linear.py

+# SPDX-License-Identifier: Apache-2.0
+
 import itertools
 from abc import abstractmethod
 from typing import Dict, List, Optional, Tuple

vllm/model_executor/layers/logits_processor.py

+# SPDX-License-Identifier: Apache-2.0
 """A layer that compute logits from hidden_stats."""
 import inspect
 from typing import Optional

vllm/model_executor/layers/mamba/mamba_mixer.py

+# SPDX-License-Identifier: Apache-2.0
+
 import torch
 from torch import nn
 from torch.nn.parameter import Parameter

vllm/model_executor/layers/mamba/ops/causal_conv1d.py

+# SPDX-License-Identifier: Apache-2.0
+
 # Copyright (c) 2024, Tri Dao.
 # Adapted from https://github.com/Dao-AILab/causal-conv1d/blob/main/causal_conv1d/causal_conv1d_interface.py
 

vllm/model_executor/layers/mamba/ops/mamba_ssm.py

+# SPDX-License-Identifier: Apache-2.0
+
 # Copyright (c) 2024, Tri Dao, Albert Gu.
 # Adapted from https://github.com/state-spaces/mamba/blob/main/mamba_ssm/ops/triton/selective_state_update.py
 

vllm/model_executor/layers/pooler.py

+# SPDX-License-Identifier: Apache-2.0
+
 from enum import IntEnum
 from typing import List, Optional, Union
 

vllm/model_executor/layers/quantization/__init__.py

+# SPDX-License-Identifier: Apache-2.0
+
 from typing import Dict, List, Type
 
 from vllm.model_executor.layers.quantization.base_config import (

vllm/model_executor/layers/quantization/aqlm.py

+# SPDX-License-Identifier: Apache-2.0
+
 # Supports AQLM compression, see https://github.com/Vahe1994/AQLM
 # and https://arxiv.org/pdf/2401.06118.pdf
 

vllm/model_executor/layers/quantization/awq.py

+# SPDX-License-Identifier: Apache-2.0
+
 from typing import Any, Dict, List, Optional
 
 import torch

vllm/model_executor/layers/quantization/awq_marlin.py

+# SPDX-License-Identifier: Apache-2.0
+
 from typing import Any, Callable, Dict, List, Optional
 
 import torch

vllm/model_executor/layers/quantization/awq_triton.py

+# SPDX-License-Identifier: Apache-2.0
+
 import torch
 import triton
 import triton.language as tl