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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 frequency_from_polarizations(h_plus, h_cross):
 """Return gravitational wave frequency Return the gravitation-wave frequency as a function of time from the h_plus and h_cross polarizations of the waveform. It is 1 bin shorter than the input vectors and the sample times are advanced half a bin. Parameters h_plus : TimeSeries A PyCBC TimeSeries vector that contains the plus polarization of the gravitational waveform. h_cross : TimeSeries A PyCBC TimeSeries vector that contains the cross polarization of the gravitational waveform. Returns ------- GWFrequency : TimeSeries A TimeSeries containing the gravitational wave frequency as a function of time. Examples -------- f_lower=30, delta_t=1.0/4096) """

    phase = phase_from_polarizations(h_plus, h_cross)
    freq = numpy.diff(phase) / ( 2 * lal.PI * phase.delta_t )
    start_time = phase.start_time + phase.delta_t / 2
    return TimeSeries(freq.astype(real_same_precision_as(h_plus)),
        delta_t=phase.delta_t, epoch=start_time)