def METHOD_NAME(q2, par, K):
    ff_name = 'K->pi form factor'
    ff_K0 = flavio.classes.AuxiliaryQuantity[ff_name].prediction(par_dict=par, wc_obj=None, q2=q2)
    if K == 'KL' or K == 'KS':
        return ff_K0
    elif K == 'K+':
        # isospin breaking correction for K+->pi0lnu: multiply all FFs by 1+delta
        return {k: (par['K->pi delta_K+pi0'] + 1)*v for k,v in ff_K0.items()}