[Misc] Fix import error in tensorizer tests and cleanup some code (#10349)

Signed-off-by: DarkLight1337 <tlleungac@connect.ust.hk>

vllm/utils.py

@@ -5,6 +5,7 @@ import datetime
 import enum
 import gc
 import getpass
+import importlib.util
 import inspect
 import ipaddress
 import os
@@ -1539,6 +1540,25 @@ def is_in_doc_build() -> bool:
         return False
 
 
+def import_from_path(module_name: str, file_path: Union[str, os.PathLike]):
+    """
+    Import a Python file according to its file path.
+
+    Based on the official recipe:
+    https://docs.python.org/3/library/importlib.html#importing-a-source-file-directly
+    """
+    spec = importlib.util.spec_from_file_location(module_name, file_path)
+    if spec is None:
+        raise ModuleNotFoundError(f"No module named '{module_name}'")
+
+    assert spec.loader is not None
+
+    module = importlib.util.module_from_spec(spec)
+    sys.modules[module_name] = module
+    spec.loader.exec_module(module)
+    return module
+
+
 # create a library to hold the custom op
 vllm_lib = Library("vllm", "FRAGMENT")  # noqa