code: def aggregate_avg(items, col):
      
      try:
          return aggregate_sum(items, col) / aggregate_count(items, col)
      except Exception:
          log.warning(c.LOGMSG_WAR_DBI_AVG_ZERODIV)
          return 0.0
docs: Function to use on Group by Charts.
          accepts a list and returns the average of the list's items