fix(python-sdk): restrict transformers version for python 3.9 compat (#36385)

* fix(python-sdk): restrict transformers version for python 3.9 compatibility

Versions 4.55.0+ use Python 3.10+ union syntax which causes TypeError on Python 3.9

* build(python): pin sentence-transformers version for python 3.9 compatibility

Use sentence-transformers 2.x for Python 3.9 to maintain compatibility with transformers <4.55.0, while allowing newer versions for Python 3.10+

* docs: add Apache license header to test file

Add required license header to comply with Apache Software Foundation requirements

Author: liferoad

sdks/python/setup.py

@@ -166,7 +166,11 @@ def cythonize(*args, **kwargs):
     'embeddings',
     'onnxruntime',
     'langchain',
-    'sentence-transformers',
+    # sentence-transformers 3.0+ requires transformers 4.34+
+    # which uses Python 3.10+ union syntax
+    # Use 2.x versions for Python 3.9 compatibility with transformers <4.55.0
+    'sentence-transformers>=2.2.2,<3.0.0; python_version < "3.10"',
+    'sentence-transformers>=2.2.2; python_version >= "3.10"',
     'skl2onnx',
     'pillow',
     'pyod',
@@ -581,7 +585,11 @@ def get_portability_package_data():
           'torch': ['torch>=1.9.0,<2.8.0'],
           'tensorflow': ['tensorflow>=2.12rc1,<2.21'],
           'transformers': [
-              'transformers>=4.28.0,<4.56.0',
+              # Restrict transformers to <4.55.0 for Python 3.9 compatibility
+              # Versions 4.55.0+ use Python 3.10+ union syntax (int | None)
+              # which causes TypeError on Python 3.9
+              'transformers>=4.28.0,<4.55.0; python_version < "3.10"',
+              'transformers>=4.28.0,<4.56.0; python_version >= "3.10"',
               'tensorflow>=2.12.0',
               'torch>=1.9.0'
           ],