'Return the zeros of the spline.
Restriction: only cubic splines are supported by fitpack.'

def roots(self):

    k = self._data[5]
    if (k == 3):
        (z, m, ier) = dfitpack.sproot(*self._eval_args[:2])
        if (not (ier == 0)):
            raise ValueError(('Error    code    returned    by    spalde:    %s' % ier))
        return z[:m]
    raise NotImplementedError('finding    roots    unsupported    for    non-cubic    splines')
