docs: def read_stats(self, *stats):
          """ Read stream statistics from chassis.
  
          :param stats: list of requested statistics to read, if empty - read all statistics.
          """
          from ixexplorer.ixe_stream import IxePacketGroupStream
          sleep_time = 0.1  # in cases we only want few counters but very fast we need a smaller sleep time
          if not stats:
              stats = [m.attrname for m in IxePgStats.__tcl_members__ if m.flags & FLAG_RDONLY]
              sleep_time = 1
  
          # Read twice to refresh rate statistics.
          for port in self.tx_ports_streams:
              port.api.call_rc('streamTransmitStats get {} 1 4096'.format(port.uri))
          for rx_port in self.rx_ports:
              rx_port.api.call_rc('packetGroupStats get {} 0 65536'.format(rx_port.uri))
          time.sleep(sleep_time)
  
          self.statistics = OrderedDict()
          for tx_port, streams in self.tx_ports_streams.items():
              for stream in streams:
                  stream_stats = OrderedDict()
                  tx_port.api.call_rc('streamTransmitStats get {} 1 4096'.format(tx_port.uri))
                  stream_tx_stats = IxeStreamTxStats(tx_port, stream.index)
                  stream_stats_tx = {c: v for c, v in stream_tx_stats.get_attributes(FLAG_RDONLY).items()}
                  stream_stats['tx'] = stream_stats_tx
                  stream_stat_pgid = IxePacketGroupStream(stream).groupId
                  stream_stats_pg = pg_stats_dict()
                  for port in self.session.ports.values():
                      stream_stats_pg[str(port)] = OrderedDict(zip(stats, [-1] * len(stats)))
                  for rx_port in self.rx_ports:
                      if not stream.rx_ports or rx_port in stream.rx_ports:
                          rx_port.api.call_rc('packetGroupStats get {} 0 65536'.format(rx_port.uri))
                          pg_stats = IxePgStats(rx_port, stream_stat_pgid)
                          stream_stats_pg[str(rx_port)] = pg_stats.read_stats(*stats)
                  stream_stats['rx'] = stream_stats_pg
                  self.statistics[str(stream)] = stream_stats
          return self.statistics