def METHOD_NAME(self, harmonics):
    try:
        n_rf = len(harmonics)
    except TypeError:
        n_rf = 1
        harmonics = [harmonics]
    if self.harmonic not in harmonics:
        raise AttributeError("self.harmonic not in harmonics")
    if not hasattr(self, 'domega'):
        raise AttributeError("""domega has not yet been calculated, 
                             calc_delta_omega must be called first""")
    if n_rf == 1:
        return (self.timebase, self.dphi), (self.timebase, self.domega)
    else:
        extendTuple = ([self.timebase[0], self.timebase[-1]], [0, 0])
        return (tuple([self.timebase, self.dphi]
                      if self.harmonic == harmonics[i]
                      else extendTuple for i in range(n_rf)),
                tuple([self.timebase, self.domega]
                      if self.harmonic == harmonics[i]
                      else extendTuple for i in range(n_rf)))