annotation contains a newline

import itertools

from sage.rings.all import Integer, PolynomialRing, QuadraticField
from sage.matrix.all import matrix
from sage.misc.all import cached_function
from sage.modules.all import vector


def conj(x):
    return x.map_coefficients(lambda c: c.conjugate())


@cached_function
def _theta_term(a, b):
    K = QuadraticField(-1, name='i')
    i = K.gen()
    R = PolynomialRing(K, names='s1, s2, t1, t2')
    s1, s2, t1, t2 = R.gens()
    S = PolynomialRing(R, names='z11, z12, z21, z22')
    Z = matrix(2, S.gens())

    s = s1 + s2 * i
    t = t1 + t2 * i

    g = vector([s, t])
    a = vector(a)
    b = vector(b)
    v1 = (g + (1 + i) * a / Integer(2))
    c = (1 + i) * b * g / Integer(2)
    return v1.apply_map(conj) * Z * v1 + c + conj(c)