code: def abs_energy(self, x):
          
          _energy = feature_calculators.abs_energy(x)
          logging.debug("abs energy by tsfresh calculated")
          return _energy
docs: As in tsfresh `abs_energy <https://github.com/blue-yonder/tsfresh/blob/master/tsfresh/feature_extraction/\
          feature_calculators.py#L390>`_ \
          Returns the absolute energy of the time series which is the sum over the squared values\
          
  
          .. math:: 
          
              E=\\sum_{i=1,\ldots, n}x_i^2
          
          
          :param x: the time series to calculate the feature of
          :type x: pandas.Series
          :return: the value of this feature
          :rtype: float