docs: def _calc_percent_disk_stats(self, stats):
          """Calculate a percentage of used disk space for data and metadata"""
          mtypes = ['data', 'metadata']
          percs = {}
          for mtype in mtypes:
              used = stats.get('docker.{0}.used'.format(mtype))
              total = stats.get('docker.{0}.total'.format(mtype))
              free = stats.get('docker.{0}.free'.format(mtype))
              if used and total and free and ceil(total) < free + used:
                  self.log.debug('used, free, and total disk metrics may be wrong, '
                                 'used: %s, free: %s, total: %s',
                                 used, free, total)
                  total = used + free
              try:
                  if isinstance(used, int):
                      percs['docker.{0}.percent'.format(mtype)] = round(100 * float(used) / float(total), 2)
                  elif isinstance(free, int):
                      percs['docker.{0}.percent'.format(mtype)] = round(100 * (1.0 - (float(free) / float(total))), 2)
              except ZeroDivisionError:
                  self.log.error('docker.{0}.total is 0, calculating docker.{1}.percent'
                                 ' is not possible.'.format(mtype, mtype))
          return percs