[BUG] exclude adds keys to the resulted tensordict

[btx0424]

Describe the bug

tensordict.exclude unexpectedly adds a key to exclude to the result if the key is a nested key.

To Reproduce

Running

import torch
from tensordict import TensorDict

next_td = TensorDict({
    'a': {
        'b': torch.zeros(64, 1),
        'c': torch.zeros(64, 1),
    },
}, [64])
next_preset = TensorDict({
    "d": torch.zeros(64, 3),
}, [64])
td = next_preset.exclude(("a", "b"))

print(td.keys(True, True))
print(td)

will raise an exception because "a" somehow became a key of td.

Importantly, it causes error for

# TransformedEnv
def _step(self, tensordict: TensorDictBase) -> TensorDictBase:
    tensordict = tensordict.clone(False)
    next_preset = tensordict.get("next", None)
    tensordict_in = self.transform.inv(tensordict)
    next_tensordict = self.base_env._step(tensordict_in)
    if next_preset is not None:
        # tensordict could already have a "next" key
        # this could be done more efficiently by not excluding but just passing
        # the necessary keys
        next_tensordict.update(
            next_preset.exclude(*next_tensordict.keys(True, True))
        )
    self.base_env._complete_done(self.base_env.full_done_spec, next_tensordict)
    # we want the input entries to remain unchanged
    next_tensordict = self.transform._step(tensordict, next_tensordict)
    return next_tensordict

when next_preset is not None.

Reason and Possible fixes

It seems like a typo in _td.py.

def _exclude(self, ...):
    ...
    if keys_to_exclude is not None:
        for key, cur_keys in keys_to_exclude.items():
            val = _tensordict.get(key, None)
            if val is not None:
                val = val._exclude(
                    *cur_keys, inplace=inplace, set_shared=set_shared
                )
            # missing indent
            if not in place:
                _tensordict[key] = val # this would add the key to the result

Checklist

• I have checked that there is no similar issue in the repo (required)
• I have read the documentation (required)
• I have provided a minimal working example to reproduce the bug (required)

[vmoens]

Should be easy to fix, let me patch this!