docs: def merge_infos(info1, info2):
      """We often need to aggregate together multiple infos. Most keys can
      just be clobbered by the new info, but e.g. any keys which contain
      counts should be added. The merge schema is indicated by the key
      namespace.
  
      Namespaces:
  
      - stats.timers: Timing
      - stats.gauges: Gauge values
      - stats.*: Counts of a quantity
      """
      for key, value in six.iteritems(info2):
          if key in info1 and key.startswith('stats'):
              if key.startswith('stats.timers'):
                  # timer
                  info1[key] += value
              elif key.startswith('stats.gauges'):
                  # gauge
                  info1[key] = value
              else:
                  # counter
                  info1[key] += value
          else:
              info1[key] = value