code: def prep_for_graph(data_frame, series=None, delta_series=None, smoothing=None,
                     outlier_stddev=None):
      
      series = series or []
      delta_series = delta_series or []
      graph = calc_deltas(data_frame, delta_series)
  
      for s in series + delta_series:
          if smoothing:
              graph[s] = graph[s].resample(smoothing)
          if outlier_stddev:
              graph[s] = remove_outliers(graph[s], outlier_stddev)
  
      return graph[series + delta_series]
docs: Prepare a dataframe for graphing by calculating deltas for
      series that need them, resampling, and removing outliers.