`cachetools` issue with `func.clear_cache()` hints

Issue is present in version 6.2.0 and 6.2.1.

Pyright complains of `reportFunctionMemberAccess` issue in this example:

```python
import cachetools.func

@cachetools.func.ttl_cache(ttl=60 * 20)  # Cache for 20m.
def square(x):
    return x * x

square.cache_clear() # pyright issue is here (reportFunctionMemberAccess).
```