def METHOD_NAME(self, series_ring, base_ring):
    """
    Returns the cycle index series of this species.
    EXAMPLES::
        sage: P = species.PermutationSpecies()
        sage: F = P + P
        sage: F.generating_series()[:5]
        [2, 2, 2, 2, 2]
    """
    return (self.left_summand().generating_series(base_ring) +
            self.right_summand().generating_series(base_ring))