internal state.

    Parameters
    ----------
    seed : int, sequence, 'default', optional
        If 'default', the random seed is reset to a default value.

        If `seed` is a sequence containing 55 floating-point numbers
        in range [0,1], these are used to set the internal state of
        the generator.

        If the value is an integer, the internal state is obtained
        from `numpy.random.RandomState` (MT19937) with the integer
        used as the initial seed.

        If `seed` is omitted (None), ``numpy.random.rand`` is used to
        initialize the generator.

    