I would write the following code:
```python
url_name_args = []

def get_url_name_args(self):
    """"
    Returns a list of arguments to build the url.
    """"
    if self.url_name_args:  # Caches an empty list or None
        return self.url_name_args
```
Normally one should use "is None" for the case that the default is None and the value was changed to False. But in this case the default is an empty list and the only valid value is a list.