add how-to-guide for hyper param optim with optuna.

[janfb]

Adding a minimal working example for using optuna for optimizing NN hyperparameters.

@swag2198 I added you as a reviewer here because I think that you have been working with optuna. Would be great to get your review on whether this guide is useful.

[codecov]

❌ 1 Tests Failed:

Tests completed	Failed	Passed	Skipped
5816	1	5815	146

View the full list of 1 ❄️ flaky test(s)

tests/torchutils_test.py::TorchUtilsTest::test_searchsorted

Flake rate in main: 42.53% (Passed 50 times, Failed 37 times)

Stack Traces | 0.005s run time

.venv/lib/python3.10....../site-packages/xdist/remote.py:289: in pytest_runtest_logreport
    self.sendevent("testreport", data=data)
.venv/lib/python3.10....../site-packages/xdist/remote.py:126: in sendevent
    self.channel.send((name, kwargs))
.venv/lib/python3.10....................................................../site-packages/execnet/gateway_base.py:912: in send
    self.gateway._send(Message.CHANNEL_DATA, self.id, dumps_internal(item))
.venv/lib/python3.10....................................................../site-packages/execnet/gateway_base.py:1629: in dumps_internal
    return _Serializer().save(obj)  # type: ignore[return-value]
.venv/lib/python3.10....................................................../site-packages/execnet/gateway_base.py:1647: in save
    self._save(obj)
.venv/lib/python3.10....................................................../site-packages/execnet/gateway_base.py:1667: in _save
    dispatch(self, obj)
.venv/lib/python3.10....................................................../site-packages/execnet/gateway_base.py:1744: in save_tuple
    self._save(item)
.venv/lib/python3.10....................................................../site-packages/execnet/gateway_base.py:1667: in _save
    dispatch(self, obj)
.venv/lib/python3.10....................................................../site-packages/execnet/gateway_base.py:1740: in save_dict
    self._write_setitem(key, value)
.venv/lib/python3.10....................................................../site-packages/execnet/gateway_base.py:1734: in _write_setitem
    self._save(value)
.venv/lib/python3.10....................................................../site-packages/execnet/gateway_base.py:1667: in _save
    dispatch(self, obj)
.venv/lib/python3.10....................................................../site-packages/execnet/gateway_base.py:1740: in save_dict
    self._write_setitem(key, value)
.venv/lib/python3.10....................................................../site-packages/execnet/gateway_base.py:1734: in _write_setitem
    self._save(value)
.venv/lib/python3.10....................................................../site-packages/execnet/gateway_base.py:1667: in _save
    dispatch(self, obj)
.venv/lib/python3.10....................................................../site-packages/execnet/gateway_base.py:1740: in save_dict
    self._write_setitem(key, value)
.venv/lib/python3.10....................................................../site-packages/execnet/gateway_base.py:1734: in _write_setitem
    self._save(value)
.venv/lib/python3.10....................................................../site-packages/execnet/gateway_base.py:1667: in _save
    dispatch(self, obj)
.venv/lib/python3.10....................................................../site-packages/execnet/gateway_base.py:1740: in save_dict
    self._write_setitem(key, value)
.venv/lib/python3.10....................................................../site-packages/execnet/gateway_base.py:1734: in _write_setitem
    self._save(value)
_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 

self = <execnet.gateway_base._Serializer object at 0x7f6d38ccc040>
obj = tensor([0.0000, 0.1111, 0.2222, 0.3333, 0.4444, 0.5556, 0.6667, 0.7778, 0.8889])

    def _save(self, obj: object) -> None:
        tp = type(obj)
        try:
            dispatch = self._dispatch[tp]
        except KeyError:
            methodname = "save_" + tp.__name__
            meth: Callable[[_Serializer, object], None] | None = getattr(
                self.__class__, methodname, None
            )
            if meth is None:
>               raise DumpError(f"can't serialize {tp}") from None
E               execnet.gateway_base.DumpError: can't serialize <class 'torch.Tensor'>

.venv/lib/python3.10....................................................../site-packages/execnet/gateway_base.py:1665: DumpError

To view more test analytics, go to the Test Analytics Dashboard
_{📋 Got 3 mins? Take this short survey to help us improve Test Analytics.}

[janfb]

Pushed improvements based on private feedback from @swag2198 🙏

[dgedon]

Overall structure is approved. I suggest some cosmetics.

[janfb]

Thanks for the review @dgedon , agree with all comments and addressed them.