Cythonized project throws an error "ValueError(f"@on function '{func_name}' must be async")"

#### Wave SDK Version, OS

wave-0.17.0-linux-amd64, Linux

#### Actual behavior

When Cythonize a project, if it has used `@on` decorators [like this](https://wave.h2o.ai/docs/examples/routing) it raises an error,

> ValueError(f"@on function '{func_name}' must be async")

#### Expected behavior

Cythonized project should work as non-cythonized project

#### Steps To Reproduce

1. Run [Routing example](https://wave.h2o.ai/docs/examples/routing) locally
2. Cythonize the project
3. Run Cythonized project locally
4. See error

```(venv) nayananga@nayananga-Aspire-E5-575G:~/Downloads/Compressed/wave-0.17.0-linux-amd64/examples/build/lib.linux-x86_64-3.8/examples$ wave run routing
INFO: Uvicorn running on http://127.0.0.1:8000 (Press CTRL+C to quit)
INFO: Started reloader process [895815] using statreload
Process SpawnProcess-1:
Traceback (most recent call last):
File "/usr/lib/python3.8/multiprocessing/process.py", line 315, in _bootstrap
self.run()
File "/usr/lib/python3.8/multiprocessing/process.py", line 108, in run
self._target(*self._args, **self._kwargs)
File "/home/nayananga/Downloads/Compressed/wave-0.17.0-linux-amd64/examples/venv/lib/python3.8/site-packages/uvicorn/subprocess.py", line 61, in subprocess_started
target(sockets=sockets)
File "/home/nayananga/Downloads/Compressed/wave-0.17.0-linux-amd64/examples/venv/lib/python3.8/site-packages/uvicorn/main.py", line 419, in run
loop.run_until_complete(self.serve(sockets=sockets))
File "/usr/lib/python3.8/asyncio/base_events.py", line 616, in run_until_complete
return future.result()
File "/home/nayananga/Downloads/Compressed/wave-0.17.0-linux-amd64/examples/venv/lib/python3.8/site-packages/uvicorn/main.py", line 426, in serve
config.load()
File "/home/nayananga/Downloads/Compressed/wave-0.17.0-linux-amd64/examples/venv/lib/python3.8/site-packages/uvicorn/config.py", line 328, in load
self.loaded_app = import_from_string(self.app)
File "/home/nayananga/Downloads/Compressed/wave-0.17.0-linux-amd64/examples/venv/lib/python3.8/site-packages/uvicorn/importer.py", line 20, in import_from_string
module = importlib.import_module(module_str)
File "/usr/lib/python3.8/importlib/__init__.py", line 127, in import_module
return _bootstrap._gcd_import(name[level:], package, level)
File "", line 1014, in _gcd_import
File "", line 991, in _find_and_load
File "", line 975, in _find_and_load_unlocked
File "", line 671, in _load_unlocked
File "", line 1174, in exec_module
File "", line 219, in _call_with_frames_removed
File "routing.py", line 8, in init examples.routing
File "/home/nayananga/Downloads/Compressed/wave-0.17.0-linux-amd64/examples/venv/lib/python3.8/site-packages/h2o_wave/routing.py", line 82, in wrap
raise ValueError(f"@on function '{func_name}' must be async")
ValueError: @on function 'clear_cart' must be async
```