NumPy compatibility in indexing.

[BalzaniEdoardo]

Trying to expand the axis of a TsdFrame results in a pandas error.
Probably what we want is to drop the metadata and expand the dimensions with no errors.

In [5]: nap.TsdFrame(t=np.arange(10),d=np.ones((10, 2)))[:,None]
---------------------------------------------------------------------------
ValueError                                Traceback (most recent call last)
...

File ~/.pyenv/versions/3.11.8/envs/pynajax/lib/python3.11/site-packages/pandas/core/indexers/utils.py:341, in disallow_ndim_indexing(result)
    333 """
    334 Helper function to disallow multi-dimensional indexing on 1D Series/Index.
    335 
   (...)
    338 in GH#30588.
    339 """
    340 if np.ndim(result) > 1:
--> 341     raise ValueError(
    342         "Multi-dimensional indexing (e.g. `obj[:, None]`) is no longer "
    343         "supported. Convert to a numpy array before indexing instead."
    344     )

ValueError: Multi-dimensional indexing (e.g. `obj[:, None]`) is no longer supported. Convert to a numpy array before indexing instead.

Also,

nap.TsdTensor(np.arange(10), np.random.randn(10,1,2))[None]

Result in another error:

ValueError: The truth value of an array with more than one element is ambiguous. Use a.any() or a.all()

In this case the expected behavior would probably be, returning a numpy array with an extra dimension added to the first axis.

as in

nap.TsdTensor(np.arange(10), np.random.randn(10,1,2)).d[None].shape
Out[52]: (1, 10, 1, 2)