Hey, may I ask a Rust generic question here?

I'm trying to port this Python code to Rust, but I'm having trouble with the inheritance and the default implementation of a method in the base class.

```python
class BaseCommand:
    def init(self, a, b):
        self.a = a self.b = b

    def execute(self):
        return self.a + self.b

class CustomCommand(BaseCommand):
    def init(self):
        super().init(1, 2)

cc = CustomCommand().execute()
```

The thing is that if I use traits I can't have default implementations that access struct fields. What's the best way to do this in Rust?