code: def _check_timeindex(self):
          
          try:
              self.timeseries.generation_fluctuating
              self.timeseries.generation_dispatchable
              self.timeseries.load
              self.timeseries.generation_reactive_power
              self.timeseries.load_reactive_power
          except:
              message = 'Time index of feed-in and load time series does ' \
                        'not match.'
              logging.error(message)
              raise KeyError(message)
docs: Check function to check if all feed-in and load time series contain
          values for the specified time index.