I came across an h5py tutorial wherein a particular index of an hdf5 file is accessed as follows:

```
f = h5py.File('random.hdf5', 'r')
data = f['default'][()]
f.close()

print(data[10])

```

In this manner, even when the file is closed, the data is still accessible. It seems adding `[()]` no longer makes `data` a simple pointer, but rather the data object itself. What is the meaning of `[()]`?