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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def calibration_lines(freqs, data, tref=None):
 """ Extract the calibration lines from strain data. Parameters freqs: list List containing the frequencies of the calibration lines. data: pycbc.types.TimeSeries Strain data to extract the calibration lines from. tref: {None, float}, optional Reference time for the line. If None, will use data.start_time. Returns ------- data: pycbc.types.TimeSeries The strain data with the calibration lines removed. """

    if tref is None:
        tref = float(data.start_time)
    for freq in freqs:
        measured_line = matching_line(freq, data, tref,
                                      bin_size=data.duration)
        data -= measured_line.data.real

    return data