.RandomState` instance.

Parameters
----------
seed : {None, int, `numpy.random.Generator`, `numpy.random.RandomState`}, optional
    If `seed` is None (or `np.random`), the `numpy.random.RandomState`
    singleton is used.
    If `seed` is an int, a new ``RandomState`` instance is used,
    seeded with `seed`.
    If `seed` is already a ``Generator`` or ``RandomState`` instance then
    that instance is used.

Returns
-------
seed : {`numpy.random.Generator`, `numpy.random.RandomState`}
    Random number generator.

