<s>[INST] ```python
import collections

class TestClass:
    def __init__(self):
        self._data = {}

    def __getattr__(self, name):
        return self._data.get(name)

    def __setattr__(self, name, value):
        if name == '_data':
            super().__setattr__(name, value)
        else:
            self._data[name] = value

    def keys(self):
        return self._data.keys()

    def nested_keys(self):
        return self.keys()

    def __str__(self):
        return f"TestClass({self._data})"

test_obj = TestClass()
test_obj.key1 = 'value1'
test_obj.key2 = 'value2'
print(test_obj.key1)
print(test_obj.key2)
```

I am trying to combine attributes access with dict like data access (key-value store) behavior in one class. The above code provides attribute- dict balanced data access. I want to be able to control fine grain data access via a class method

When you look at the given code, we can see `nested_keys()` is a replica of the `keys()` method. The main idea is to implement data access at more than one nesting level using `nested_keys()` and `key` value assignment at more than one nesting level using attribute access (`test_obj.attr.key1`) 

**Q**: How to modify this code so `nested_keys()` should return all keys at any nesting level?[/INST]