the integral of modular forms

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I compute the integral of modular forms using the PARI command in SageMath as follows.

def phi(s, t):
    mf = pari.mfinit([27, 2], 0)
    f = pari.mfeigenbasis(mf)[0]
    symb = pari.mfsymbol(mf, f)
    F = pari.mfsymboleval(symb, [s,t]) * 2 * pi * I
    return F

but the results show that phi(oo,0)+phi(0,a)=-phi(oo,a) where a is the cubic root of unity in the upper half plane.

Should it be phi(oo,0)+phi(0,a)=phi(oo,a)? What is the reason?