code: def _init_dataframes(self):
          
          df = pd.read_sql_query("SELECT elapsed, epoch, scriptrun_time, custom_timers FROM result ORDER BY epoch ASC",
                                 db.get_conn())
  
          self._get_all_timers(df)
          self.main_results = self._get_processed_dataframe(df)
  
          # create all custom timers dataframes
          for key, value in six.iteritems(self._timers_values):
              df = pd.DataFrame(value, columns=['epoch', 'scriptrun_time'])
              df.index = pd.to_datetime(df['epoch'], unit='s')
              timer_results = self._get_processed_dataframe(df)
              self.timers_results[key] = timer_results
  
          # clear memory
          del self._timers_values
docs: Initialise the main dataframe for the results and the custom timers dataframes