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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 sigma(htilde, psd = None, low_frequency_cutoff=None, high_frequency_cutoff=None):
 """ Return the sigma of the waveform. See sigmasq for more details. Parameters htilde : TimeSeries or FrequencySeries The input vector containing a waveform. psd : {None, FrequencySeries}, optional The psd used to weight the accumulated power. low_frequency_cutoff : {None, float}, optional The frequency to begin considering waveform power. high_frequency_cutoff : {None, float}, optional The frequency to stop considering waveform power. Returns ------- sigmasq: float """

    return sqrt(sigmasq(htilde, psd, low_frequency_cutoff, high_frequency_cutoff))