code: def line_model(freq, data, tref, amp=1, phi=0):
      
      freq_line = TimeSeries(zeros(len(data)), delta_t=data.delta_t,
                             epoch=data.start_time)
  
      times = data.sample_times - float(tref)
      alpha = 2 * numpy.pi * freq * times + phi
      freq_line.data = amp * numpy.exp(1.j * alpha)
  
      return freq_line
docs: Simple time-domain model for a frequency line.
  
      Parameters
      ----------
      freq: float
          Frequency of the line.
      data: pycbc.types.TimeSeries
          Reference data, to get delta_t, start_time, duration and sample_times.
      tref: float
          Reference time for the line model.
      amp: {1., float}, optional
          Amplitude of the frequency line.
      phi: {0. float}, optional
          Phase of the frequency line (radians).
  
      Returns
      -------
      freq_line: pycbc.types.TimeSeries
          A timeseries of the line model with frequency 'freq'. The returned
          data are complex to allow measuring the amplitude and phase of the
          corresponding frequency line in the strain data. For extraction, use
          only the real part of the data.