[1/2/N] Enable pymarkdown and python __init__ for lint system (#2011)

### What this PR does / why we need it?
1. Enable pymarkdown check
2. Enable python `__init__.py` check for vllm and vllm-ascend
3. Make clean code

### How was this patch tested?


- vLLM version: v0.9.2
- vLLM main:
29c6fbe58c

---------

Signed-off-by: wangli <wangli858794774@gmail.com>

tools/check_python_src_init.py

@@ -0,0 +1,75 @@
+#
+# Copyright (c) 2025 Huawei Technologies Co., Ltd. All Rights Reserved.
+# Copyright 2023 The vLLM team.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+# This file is a part of the vllm-ascend project.
+# Adapted from https://github.com/vllm-project/vllm/tree/main/tools
+#
+import os
+import sys
+
+VLLM_ASCEND_SRC = "vllm_ascend"
+VLLM_SRC = "vllm-empty/vllm"
+
+
+def check_init_file_in_package(directory):
+    """
+    Check if a Python package directory contains __init__.py file.
+    A directory is considered a Python package if it contains `.py` files and an `__init__.py` file.
+    """
+    try:
+        files = os.listdir(directory)
+    except FileNotFoundError:
+        print(f"Warning: Directory does not exist: {directory}")
+        return False
+
+    # If any .py file exists, we expect an __init__.py
+    if any(f.endswith('.py') for f in files):
+        init_file = os.path.join(directory, '__init__.py')
+        if not os.path.isfile(init_file):
+            return False
+    return True
+
+
+def find_missing_init_dirs(src_dir):
+    """
+    Walk through the src_dir and return subdirectories missing __init__.py.
+    """
+    missing_init = set()
+    for dirpath, _, _ in os.walk(src_dir):
+        if not check_init_file_in_package(dirpath):
+            missing_init.add(dirpath)
+    return missing_init
+
+
+def main():
+    all_missing = set()
+
+    for src in [VLLM_ASCEND_SRC, VLLM_SRC]:
+        missing = find_missing_init_dirs(src)
+        all_missing.update(missing)
+
+    if all_missing:
+        print(
+            "❌ Missing '__init__.py' files in the following Python package directories:"
+        )
+        for pkg in sorted(all_missing):
+            print(f" - {pkg}")
+        sys.exit(1)
+    else:
+        print("✅ All Python packages have __init__.py files.")
+
+
+if __name__ == "__main__":
+    main()