Fix performance in get_imports regexp (#34298)

* fix: Fix performance in get_imports regexp

* Minimize get_imports content regexp

src/transformers/dynamic_module_utils.py

@@ -152,7 +152,8 @@ def get_imports(filename: Union[str, os.PathLike]) -> List[str]:
         content = f.read()
 
     # filter out try/except block so in custom code we can have try/except imports
-    content = re.sub(r"\s*try\s*:\s*.*?\s*except\s*.*?:", "", content, flags=re.MULTILINE | re.DOTALL)
+    content = re.sub(r"\s*try\s*:.*?except.*?:", "", content, flags=re.DOTALL)
+
     # filter out imports under is_flash_attn_2_available block for avoid import issues in cpu only environment
     content = re.sub(
         r"if is_flash_attn[a-zA-Z0-9_]+available\(\):\s*(from flash_attn\s*.*\s*)+", "", content, flags=re.MULTILINE