code: def frequency_of_peaks(self, x, start_offset=100, end_offset=100):
          
  
          peaks_data = x[start_offset: -end_offset].values
          maxtab, mintab = peakdet(peaks_data, self.delta)
  
          x = np.mean(peaks_data[maxtab[1:,0].astype(int)] - peaks_data[maxtab[:-1,0].astype(int)])
  
          frequency_of_peaks = abs(1/x)
  
          return frequency_of_peaks
docs: This method assess the frequency of the peaks on any given 1-dimensional time series.
  
              :param x: The time series to assess freeze of gait on. This could be x, y, z or mag_sum_acc.
              :type x: pandas.Series
              :param start_offset: Signal to leave out (of calculations) from the begining of the time series (100 default).
              :type start_offset: int
              :param end_offset: Signal to leave out (from calculations) from the end of the time series (100 default).
              :type end_offset: int
              :return frequency_of_peaks: The frequency of peaks on the provided time series [measured in Hz].
              :rtype frequency_of_peaks: float