docs: def balance_to_ringchart_items(balance, account='', show=SHOW_CREDIT):
      """Convert a balance data structure into RingChartItem objects."""
      show = show if show else SHOW_CREDIT  # cannot show all in ring chart
      rcis = []
      for item in balance:
          subaccount = item['account_fragment'] if not account \
              else ':'.join((account, item['account_fragment']))
          ch = balance_to_ringchart_items(item['children'], subaccount, show)
          amount = item['balance'] if show == SHOW_CREDIT else -item['balance']
          if amount < 0:
              continue  # omit negative amounts
          wedge_amount = max(amount, sum(map(float, ch)))
          rci = gtkchartlib.ringchart.RingChartItem(
              wedge_amount,
              tooltip='{}\n{}'.format(subaccount, wedge_amount),
              items=ch
          )
          rcis.append(rci)
      return rcis