add return None statements

pythonbpf/vmlinux_parser/import_detector.py

@@ -106,19 +106,19 @@ def vmlinux_proc(tree: ast.AST, module):
 
     if not import_statements:
         logger.info("No vmlinux imports found")
-        return
+        return None
 
     # Import vmlinux module directly
     try:
         vmlinux_mod = importlib.import_module("vmlinux")
     except ImportError:
         logger.warning("Could not import vmlinux module")
-        return
+        return None
 
     source_file = inspect.getsourcefile(vmlinux_mod)
     if source_file is None:
         logger.warning("Cannot find source for vmlinux module")
-        return
+        return None
 
     with open(source_file, "r") as f:
         mod_ast = ast.parse(f.read(), filename=source_file)