def METHOD_NAME(self, deltaC, C_name):
    wc  = {'7': 0, '7p': 0, 'v': 0, 'a': 0, 's': 0, 'p': 0,
           't': 0,'vp': 0, 'ap': 0, 'sp': 0, 'pp': 0, 'tp': 0, }
    wc[C_name] = deltaC
    return flavio.physics.bdecays.angular.helicity_amps_v(self.q2,
                self.mB, self.mV, self.mb, 0,
                0, 0,  # ml=0 as this only affects scalar contributions
                self.ff, wc, self.prefactor)