docs: def most_populated(adf):
          """
          Looks at each column, using the one with the most values
          Honours the Trump override/failsafe logic. """
  
          # just look at the feeds, ignore overrides and failsafes:
          feeds_only = adf[adf.columns[1:-1]]
  
          # find the most populated feed
          cnt_df = feeds_only.count()
          cnt = cnt_df.max()
          selected_feeds = cnt_df[cnt_df == cnt]
  
          # if there aren't any feeds, the first feed will work...
          if len(selected_feeds) == 0:
              pre_final = adf['feed001'] # if they are all empty
                                    # they should all be
                                    # equally empty
          else:
              #if there's one or more, take the highest priority one
              pre_final = adf[selected_feeds.index[0]]
  
  
          # create the final, applying the override and failsafe logic...
          final_df = pd.concat([adf.override_feed000,
                                pre_final,
                                adf.failsafe_feed999], axis=1)
          final_df = final_df.apply(_row_wise_priority, axis=1)
          return final_df