[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/distributed/communication_op.py

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

vllm/distributed/device_communicators/cuda_wrapper.py

+# SPDX-License-Identifier: Apache-2.0
 """This file is a pure Python wrapper for the cudart library.
 It avoids the need to compile a separate shared library, and is
 convenient for use when we just need to call a few functions.

vllm/distributed/device_communicators/custom_all_reduce.py

+# SPDX-License-Identifier: Apache-2.0
+
 import ctypes
 from contextlib import contextmanager
 from typing import List, Optional, Union

vllm/distributed/device_communicators/custom_all_reduce_utils.py

+# SPDX-License-Identifier: Apache-2.0
+
 import ctypes
 import json
 import os

vllm/distributed/device_communicators/hpu_communicator.py

+# SPDX-License-Identifier: Apache-2.0
+
 import torch
 import torch.distributed as dist
 from torch.distributed import ProcessGroup

vllm/distributed/device_communicators/pynccl.py

+# SPDX-License-Identifier: Apache-2.0
+
 from typing import Optional, Union
 
 # ===================== import region =====================

vllm/distributed/device_communicators/pynccl_wrapper.py

+# SPDX-License-Identifier: Apache-2.0
+
 # This file is a pure Python wrapper for the NCCL library.
 # The main purpose is to use NCCL combined with CUDA graph.
 # Before writing this script, we tried the following approach:

vllm/distributed/device_communicators/shm_broadcast.py

+# SPDX-License-Identifier: Apache-2.0
+
 import os
 import pickle
 import sys

vllm/distributed/device_communicators/tpu_communicator.py

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

vllm/distributed/device_communicators/xpu_communicator.py

+# SPDX-License-Identifier: Apache-2.0
+
 import torch
 import torch.distributed as dist
 from torch.distributed import ProcessGroup

vllm/distributed/kv_transfer/kv_connector/base.py

+# SPDX-License-Identifier: Apache-2.0
 """
 KVConnectorBase Class for Distributed KV Cache & Hidden State communication
 

vllm/distributed/kv_transfer/kv_connector/factory.py

+# SPDX-License-Identifier: Apache-2.0
+
 import importlib
 from typing import TYPE_CHECKING, Callable, Dict, Type
 

vllm/distributed/kv_transfer/kv_connector/simple_connector.py

+# SPDX-License-Identifier: Apache-2.0
 """
 Simple KV Cache Connector for Distributed Machine Learning Inference
 

vllm/distributed/kv_transfer/kv_lookup_buffer/base.py

+# SPDX-License-Identifier: Apache-2.0
 """
 This file contains a new class `KVLookupBufferBase` that allows developers to 
 think of KV cache operations as inserting new KV cache entries (`insert`) 

vllm/distributed/kv_transfer/kv_lookup_buffer/simple_buffer.py

+# SPDX-License-Identifier: Apache-2.0
 """
     Implements a distributed key-value (KV) cache transfer mechanism.
 

vllm/distributed/kv_transfer/kv_pipe/base.py

+# SPDX-License-Identifier: Apache-2.0
 """
 This file defines an interface `KVPipeBase`
 that provides an abstraction for sending and receiving tensors, or None, via

vllm/distributed/kv_transfer/kv_pipe/mooncake_pipe.py

+# SPDX-License-Identifier: Apache-2.0
+
 import json
 import os
 import pickle

vllm/distributed/kv_transfer/kv_pipe/pynccl_pipe.py

+# SPDX-License-Identifier: Apache-2.0
 """
     This module implements a PyNccl pipe for sending and receiving 
     Optional[torch.Tensor] between distributed ranks with advanced 

vllm/distributed/kv_transfer/kv_transfer_agent.py

+# SPDX-License-Identifier: Apache-2.0
 """A centralized entrypoint to perform distributed KV cache transfer.
 
 This implementation is a shim wrapper on two APIs exposed by `kv_connector`:

vllm/distributed/parallel_state.py

+# SPDX-License-Identifier: Apache-2.0
+
 # Copyright 2023 The vLLM team.
 # Adapted from
 # https://github.com/NVIDIA/Megatron-LM/blob/main/megatron/core/parallel_state.py