def METHOD_NAME():
    """
    Return the species of simple graphs.
    EXAMPLES::
        sage: S = species.SimpleGraphSpecies()
        sage: S.generating_series().counts(10)
        [1, 1, 2, 8, 64, 1024, 32768, 2097152, 268435456, 68719476736]
        sage: S.cycle_index_series()[:5]
        [p[],
         p[1],
         p[1, 1] + p[2],
         4/3*p[1, 1, 1] + 2*p[2, 1] + 2/3*p[3],
         8/3*p[1, 1, 1, 1] + 4*p[2, 1, 1] + 2*p[2, 2] + 4/3*p[3, 1] + p[4]]
        sage: S.isotype_generating_series()[:6]
        [1, 1, 2, 4, 11, 34]
    TESTS::
        sage: seq = S.isotype_generating_series().counts(6)[1:]
        sage: oeis(seq)[0]                              # optional -- internet
        A000088: Number of graphs on n unlabeled nodes.
    ::
        sage: seq = S.generating_series().counts(10)[1:]
        sage: oeis(seq)[0]                              # optional -- internet
        A006125: a(n) = 2^(n*(n-1)/2).
    """
    E = SetSpecies()
    E2 = SetSpecies(size=2)
    WP = SubsetSpecies()
    P2 = E2 * E
    return WP.functorial_composition(P2)